Ball joint/disc brake conversion for 74 620

[NastyNate]

I have have found a 79' with disc and ball joint, will everything bolt right up except for the upper control arm? Or would I need to do more work than that to get it all under there?

[datzenmike]

No. Won't work, or everyone would be doing this. I would swap the '74 body onto the '79 frame if wanting disc brakes, ball joint steering/suspension, internally regulated alternator and EI (electric ignition)

[wayno]

There is a little more involved, but if done right you can make it work.

I drove a 521 with a 79 620 lower control arms, tension rods, and spindle assembly/hubs with 1990 Nissan hardbody V6 rotors/calipers, I used Nissan 720 upper control arms that were lengthened 3/4", but I had issues with the upper control arm mount bolts, they were too weenie but in the end I bought longer bolts that I could put a big washer and nuts on the back side of the tower near the shocks to keep them bolts tight, I drove it this way for years, but I also had power steering and that destroyed the frame where I had the steering gear mounted.

I decided that them upper control arm mount bolt holes needed to drilled out and threaded/tapped to use 720 mount bolts, but I never did this so I do not know if there are any issues if one does this.

If it was easy to do what you are talking about everyone would do it, but not everyone does it, but it is possible.

The biggest issue I had was the upper control arm mount bolts kept getting loose and breaking on me when I hit the brakes which totally sucks, I kept tightening them bolts till they either broke from being too tight or it stripped the threads out of the mounts and that was why I ended up with big washers and nuts on the back side.

Edited May 18, 2019 by wayno

[Stoffregen Motorsports]

Don't forget better suspension geometry, larger tension/compression rods, exposed steering shaft (column not attached to box), steering box and idler arm mounted on outside of frame (more room between frame rails).