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620KC on 720 bare frame build


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Just curious how the 720 dash fits to the windshield area. Can you please take more pictures of the 720 dash in the 620 cab, from all angles? And, please describe any mods you had to do. Thank you!! By the way, same color as the 1973 620 I have that my Dad bought brand new.



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19 hours ago, 620slodat said:

pictures of the 720 dash in the 620 cab

I'll do that. For the initial fit I only had to trim about 1/2" off each of the side mounting tabs. The outer 2 dash mounting tabs need to be relocated. I saved the brackets off the 720 so will use whichever fit best, they'll be obvious in the pics due to different color. Curve of the dash to windshield appears good, if there is a difference the gap will be small enough I should be able to use weather stripping.

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  • 2 weeks later...

Started to work on the body, need to repair the body mounts in the cab before I can fit the cab around the power steering and any other protrusions. 



Luck was on my side and found the near perfect balance point hoisting the cab with my gantry. Anyway the cab needs some attention in many spots but overall in not too bad of shape. The footwell cab mounts are pretty much gone so that's the first task.

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While I'm at this stage I wanted to figure out my rad as the 620 hoses aren't where the Z24 needs them and the 720 rad is much too wide for the 620 body without major surgery. I had no idea there are so many different radiators, and after looking at specs for over 2500 ones, I have narrowed my search down to 10 candidates. None are close enough to just fit unless they're for a much smaller displacement engine like 1.5L, which is unlikely to provide enough cooling. ARRRRGH. Still hoping to find a factory rad that will work instead of spending $$$$ on a custom aluminum one which really isn't in my budget - going to the local wreckers is. Have any of you had to get a custom rad? How expensive are they?


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Attacked the rust today with a fresh wire wheel on my grinder and found the tin-worm has been hungry. Patches will definitely need to be super-sized. Rockers are totally pooched and Left bottom of cab/rear corner had been filled with bondo previously.

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I think I have the replacement rad figured out, should have the replacement by Friday (fingers crossed).


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  • 3 weeks later...

In my efforts to get to clean metal I discovered that the rust was more serious than anticipated.

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There's nothing in the front corner to even attach to 😭

I braced the door openings in an effort to retain the dimensions and began to hack away...



This has certainly slowed my progress alot, and testing my patience. There are 2 things I don't do - bodywork and drywall taping/finishing. There's a reason... no patience.

So I have built myself a sheet metal brake and have cobbled together my first replacement floorpan. It ain't pretty but it will be covered above and below so it will do. I have welded further than these pics show, rivets were used to hold it in place and hold the parts close together for welding. I hate bodywork...


Since I don't have a bead roller, I made do with some panels that already had beads run in it to provide some additional stiffness. I did find some aftermarket replacement panels from Thailand, but due to not working in 1-1/2 years my budget has ground done to virtually nil so I'll make do with what I can scrounge plus what I'd already salvaged from the 720 donor, like rockers.


My current progress is further than these pics show. I had salvaged from the 720 a support brace that ran across the back of the cab, which is being repurposed as the actual cab support mounts. Today I will continue to rebuild the rocker support panel to the rear of the cab and then I can re-make the rear cab mount before I work on the replacement rockers themselves.


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I have found a radiator that will work for me, one from an early eighties VW Passat/Golf which is a cross-flow but both hoses are on the passenger side. The end tank is divided so the coolant flows across R to L for the upper half, then comes back L to R across the lower half. Overall it is a bit lower in height and only slightly wider than the 620 rad which means only a small trim on a interfering bracket and it'll be good to go. The rad is fitted with a port for a thermal sensor for an electric fan, so that will be added & wired u when I'm at that stage.


Big advantage to using an off-the-shelf rad vs custom is that should something ever happen, a replacement is easy to get and WAY cheaper than a custom rad. This cost me less than $100 CDN and is brand-new. I did have to add a coolant recovery tank as this rad has no means to fill. I'll post pic of that later once I have things in place as I'm not sure how much room I'll have in the engine bay.

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16 hours ago, EDM620 said:

I have found a radiator that will work for me, one from an early eighties VW Passat/Golf which is a cross-flow but both hoses are on the passenger side. The end tank is divided so the coolant flows across R to L for the upper half, then comes back L to R across the lower half. Overall it is a bit lower in height and only slightly wider than the 620 rad which means only a small trim on a interfering bracket and it'll be good to go. The rad is fitted with a port for a thermal sensor for an electric fan, so that will be added & wired u when I'm at that stage.

I was eyeing these radiators up for my eventual swap also, but then had to consider an overflow/fill point. I had half a mind to use an aluminum radiator from an Integra (honda full size, both hoses more or less on the right side) but I feel like it would be too big, and a Honda half-rad too small to cool a 2.4L. Is that VW rad a single row? And can I ask, where did you end up ordering it from?

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I used a NEW Hyundai Scoupe aluminum rad in a 510 CA18DET swap.  Inlet outlet worked well, dimensions worked well, just had to fab up some quick brackets with rubber isolators.


PS if anybody interested, I have a VERY straight, original paint, minimal rust, WITH title, 74 620 standard cab rolling shell, available here in Denver.  The front clip is PERFECT, never been hit.  All four floor pan body mounts are gone (forward rad core support mounting points look good), but KlassicFab JDM will be making those "cups" as a patch panel for rust repair pretty soon.  The drivers front floor area will need a SMALL patch, but the rest is very dry Colorado solid!  The bed is also decent, with minor rust thru along the passenger bed seam.............drivers side is pretty nice.  Again, original paint!  I bought this truck sight unseen as a parts truck, already partially stripped out............was surprised to find how solid it was!

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12 hours ago, klam07 said:

And can I ask, where did you end up ordering it from?

I used Spectra website to conduct a lot of the research as they do provide specs on their rads, I had no idea there were so many and I looked over 2500 different ones to narrow my search, planning on getting something from a wrecker. This one is two row core and found it listed by NAPA for about $350. I tried to get a quote from a local shop to rebuild the OE 620 rad knowing it would need 3 things: upper hose relocated (OE rad actually had a flat in the right spot) plus the bottom tank had taken a good hit, and of course I'd wanted it re-cored. My minimum cost for testing would have been 120 minimum, nvm the final cost. I checked out PartsAvatar and they carried same rad from Spectra but under $100 new AND months ago they opened up a local warehouse so I could also get zero freight cost. With the provision for the temp sensor I'll be able to run electric fans that will run only as needed.👍


I'll be using a small coolant recovery bottle which also gives me my fill point. The one I bought is definitely small, and I could use pretty much any OE plastic one depending on what I end up with for useable space.


The rad cap is motorcycle sized, but overall it's nice and compact so it gives me lots of options on where I can fit it in.

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As I said before, I hate doing bodywork and don't have that patience. That said, I've been chipping away at the rust repairs, started with R passenger footwell. This is my result so far


I've found that construction adhesive is an excellent seam sealer, hardens without becoming brittle. Top-coated with box liner spray.


cab corner done, bottom panel is new as well


cab support brace welded and sealed in place.

Will end up over-coating bottom of cab with proper undercoating to slow down the tin worms if not fully banished, and deaden the floor further. Inner rocker to rear of cab + R rear cab mount next on the hit list. At least all of this scabby body repairs of mine will be fully hidden!


Taking a few days off the project. Have a good Thanksgiving everyone however you'll be enjoying it.

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3 hours ago, EDM620 said:

I checked out PartsAvatar and they carried same rad from Spectra but under $100 new AND months ago they opened up a local warehouse so I could also get zero freight cost. With the provision for the temp sensor I'll be able to run electric fans that will run only as needed.👍


I'll be using a small coolant recovery bottle which also gives me my fill point. The one I bought is definitely small, and I could use pretty much any OE plastic one depending on what I end up with for useable space.


As always, thanks for the information! This is super helpful, I wasn't aware of partsavatar, or at least I didn't think they were local/canadian. Hopefully it can out-price rockauto sometimes.


edit: Im now wondering, since many have used these VW rads successfully yet they were intended for a ~1.6/1.8L engine.. if an aluminum half-rad for a Honda would work after all (1.6-1.8L as well). They're compact, no plastic tanks, and can be found with 2-3 rows for pretty inexpensive. Outlets are also 32mm and right-side biased. Not to mention have a fill point, but no temp sensor provision.
Still debating between these two options after all, lol

Edited by klam07
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6 hours ago, klam07 said:

they were intended for a ~1.6/1.8L engine

True that, and that was a concern for me in my researching what to use. A buddy who is an engineer piped into my own group discussion and in his opinion the older rad would have been less efficient plus didn't have fan shroud or even a decent fan, and add-in the fact of being able to have a high-efficiency fan that can run as needed (I'll be considering running 2 fans similar to what VW did) so I believe there shouldn't be a problem - key is to have engine operating at intended 180 F temp range, not too hot or too cold.


3 hours ago, FrankRizzo said:

Whats the specs or where did you get the overflow?

NovelBee Universal Polished Chrome Aluminum Air Catch Cooler Radiator Overflow Breather Tank Engine Coolant Can

Now there's a mouthful for a description! From Amazon. Overall Size: 7.9" x 2.5" x 3.8"

I knew it would be small but I'm guessing I won't have a lot of room to put this where I'd like it, and I can always go to a wreckers and pick out a plastic one if I have room or need a bigger one. The tiny rad cap had me concerned initially but I compared it to a buddy's water-cooled bike and saw that it was the same size, so no weirdness/Chineseium on a replacement if necessary.


As for the construction adhesive, I'd read some blogs by old school hot rodders who swore by "Liquid Nails" but I couldn't find that locally (not sure if even made anymore) so went with a similar product that will bond to metal. I let it cure overnight and it was really nice, dries hard but not brittle & can be top-coated.

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  • 2 months later...

Time for a long overdue update. Since I don't enjoy doing bodywork I've found many opportunities to avoid it but work has been going on. I wasn't happy with the floor pan I initially made so I fabbed up a new one 16ga and formed new rockers while I had access to bigger equipment.





Removed all the crap I wasn't happy with and started fresh


Not apparent but since I didn't press in any contours to eliminate booming, I welded in some reinforcements underneath plus fabbed up much better cab mounts than I initially used.


Also not visible is the inner panel that the rocker backs onto. I still have some welding to do underneath but the passenger side is largely done & I'm happier with my work.

The driver's side floor isn't as badly rotted but in different ways, so no end to the challenges.

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  • 1 month later...

Drivers floor is looking better now. 3 of the cab mounts are now rebuilt, working on the final one as time permits, then I can get the rocker mounted up and proceed to remake the remaining sections of rocker and door sills.

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I might have said this before, but bodywork is not my cup-o-tea so I find it hard to get motivated to do and more easily frustrated when it's not going well.

Soon I need to flip the cab over so I can more easily & comfortably do the underside welding.

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  • 3 weeks later...

Thanks to the shortage of work out there I find myself on the unemployed line which means I'm finding myself with ample time to work on the project again but without the funds to buy shiny new things. Seems that Time & Money are never in abundance together...


Anyway, realizing previously that I was going to need to get at the underside to complete the welding of the cab mounts, it was time to ponder and get the 2 brain cells off their asses, so I got me a pen and some paper... and drafted out some ideas based on some stuff I saw while surfin' the net.

The end result works pretty good - keep in mind the cab weighs only about 660 pounds, so the weight isn't really an issue for the lumber.




The ends are located using UniStrut which is adjustable and will allow me to use this for when I do the bodywork on the box. The pivot point for the cab is higher than I'd estimated, so I may add in some adjustability to get the weight in better balance. Maybe. I really don't think I'll need it up on this for too long so I may not get to the need.

The casters allow me to move it about in my shop for extra space while I'm cursing about how much I love doing bodywork.


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On 9/4/2020 at 10:42 PM, EDM620 said:

I was also able to fit up the dash and will be going forward with the 720 dash. Next I have to determine if I can use the 720 heater/blower assembly as the squirrel cage blower is wider (& moves more air).



Soon I'll be spending some quality time with my welder and grinder...


OMG I did this on my 620 KC. I fit it to an '82 long box frame. I think the dash was an '85, the wiring harness was an '82? Had to get rid of the 620 heater and cover the fresh air inlet hole and cut a new one over on the far passenger side. To mount the 720 heater fan box I had to relocate the wiper outside the cab in the plenum. The 720 heater went in and there was a triangular 4" hose to connect the fan to it. If there was air con, this is where it went. Then in went the 720 steering column so the headlight/signals and the wiper switch on the column could be used. The 720 dash fits the bottom of the windshield very closely.




The steering wheel is from a 280zx. The 720 steering column allowed me to use a 280zx power steering box on the end.


With 4x4 gauges and console 



Found one with the clock/tach options.



All 720 had the pulse delay wipers but the delay was fixed. I found the variable delay switch and the amplifiers for it and wired it in. The first ON position is variable by twisting the end cap, up to 15 seconds? then the two speeds



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Thanks Mike for sharing those pics. My instrument cluster has the tach (maybe all did or this did because of manual trans) but just an ugly blank spot where the clock would be. Perhaps a future boost gauge or??


When I did the test fit, I noted that the dash curve appears to be very close to the 620 windshield curve, only real difference is the outer 2 upper attachment points are a few inches further apart on the 720 dash. I saved the mounting tabs from the 720 so I can pop those into the correct spots. How did you manage yours?


Looking at the wiper motor, I noted the difference in location as well as the 720 motor plug has a slight configuration difference, no doubt due to the added intermittent speed feature. I will be using the full 720 wiring harness (selectively trimmed of unneeded circuits) so things should be essentially plug & play. Steering column will be the 720, still early to fit up but I'm assuming the passage through the firewall will be essentially the same position/opening.


General question for everyone - the truck had an aftermarket sunroof that amazingly hadn't leaked, but the gasket is pretty much rotted away. Any idea where I could source replacement gasket rubber? I'd like to retain the sunroof if possible.


Terribly cold outside today (-30C/-22F) so I might take a couple days off from working in the garage as the floor will still be freaking cold.

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  • 3 weeks later...

Well I have a dilemma. The cab had an aftermarket pop-up sunroof put in some years ago but the gasket is rotted away. Amazingly it hadn't leaked. Problem is these sunroofs have vanished from the marketplace long ago and the original gasket is NLA. So what do I do about the big hole. Cheapest option was to replace the gasket but my searches have turned up nothing.


Next option is to make a patch panel (I saved a roof skin off a regular cab) but with that runs the risk of roof warpage. 3rd option is to bite the bullet and fork over $ for a new aftermarket sunroof (Hollandia 100) or even more $$ for a Hollandia 300 spoiler type.


Another option is to do a full roof cut (looking at a Tiburon sunroof) and try to graft that on, but same risk of warpage PLUS leading edge looks like it has more curve than the 620 roof.


What do you guys think about this? Is there another option I haven't thought of?

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Today I managed to get the 720 dash fitted up and made the necessary brackets (shades of Binky) to secure it. The only 620 OE bracket that was useful was the center at the forward edge, the outer ones aren't far enough apart to fit the 720 dash. I recently invested in Cleco's and am sure glad I did, they make positioning brackets repeatable. For some reason I thought Cleco's were expensive, but they're actually pretty cheap.

Dash is really solid, with all 7 mounts (3 across the top, 1 at steering column, 1 behind glove box, and the 2 lower outer corners). 




The chunk of wood filler for the hack job that tried to put in a stereo - something to deal with later.


I next setup the seats I'd sourced from my local wrecker, to make sure of fit before I went further, and in mock up they look decent.


Initially I took the passenger seat apart further than what was necessary (duh) but that gave me better access to make sure I located everything correctly.


Happy with the outcome on the passenger seat, next is the drivers seat which will be even easier to do now.


What to do tomorrow??

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On 9/5/2020 at 8:08 PM, 620slodat said:

Just curious how the 720 dash fits to the windshield area.

The 720 dash looks like a near perfect fit to the windshield, the 720 dash is about 3/4" wider than the available space due to difference in how they were mounted. First hurdle was the 2 outer top brackets as the only 620 bracket that was useable was the center, all others had to be made.

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I think I trimmed each side to fit. Didn't try to bolt anything down along the windshield ledge, worked fine without. Relocated the wiper into the plenum so I could install the 720 heater fan. (I think it's the 620 wiper) No way around this if you want the fan. Had to cut a new air inlet for the fan and seal the 620's center one. Got the tack and clock options... they are plug and play. Another thing was the variable pulse delay wipers. Stock they have a fixed delay position marked MIST. The variable used a different amplifier and two added wires. BTW the wiper motor is not different for delay wipers. The delay is built into the amplifier and in effect is the same as if someone was turning the wiper on for 1/2 a second to get it moving and is immediately in park mode and after finishing the wipe, parks itself and waits.

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  • EDM620 changed the title to 620KC on 720 bare frame build

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