I've done it. It was a waste of time and kind of hacked in. I cut the lower control arm mounts off the 7.5 and welded them to the 8.5 in the correct location. Then i drilled new holes in the upper control arm mounts to effectively shorten them and make them farther apart to bolt onto the wider 8.5 uca ears. Then i got wheels with more offset depth because the 8.5 is wider. It worked fine. I stuck a new set of 4.10s in it on the original posi that came with the junkyard 8.5. I think it was from a 77 cutlass. I've also swapped in a 8.5 GN diff and that was much better. Now i have a home built 9". The 8.5 that i originally swapped in came with bolt-in axles which was nice and kinda rare. That diff did eventually run high 10's with a nitrous big block on the stock posi / axles. This was all on a friends 78 malibu that is now long gone.
brian
