720 Parts in 620?

[Zeyemurgy]

Okay, I've got a complete '82 720 KC diesel doner truck (on craigslist at the moment, unless what I want to do is possible...) that I need to know if the transmission, FS5W71B HE38 w/driver-side starter, can somehow be made to fit into my '73 620 with an L16, passenger-side starter, and if the rear-gears will fit into either my '73 or '77 620?

I'm looking to maximize mpg, if the parts will fit.

Thanks.

[yello620]

Sorry, cant answer the transmission question, but the gears will fit in either of the 620's. there is a tag on the right side of the engine bay that tells you what gears are in the 720. Both 620's should be 4.375 gears stock. Prefered gears in my 620 is the current 3.89 gears. I have tried 4.375, 4.11, and 3.70. I am currently seeing about 23-25 mpg, that is not trying to maximize my mileage either.

[datzenmike]

The quick answer is no to the tranny. Different motors, won't bolt up. In addition, the very early 620s with L16 usually had a short 4 spd. tranny very like the 510 goon. The 720 Diesel tranny will be much longer.