I put a posi 10 bolt 8.5 into my 72 chevelle,from a 86 caprice wagon (heavy duty), I cut off and rewelded all the mounts. It fits fine, the rearend is only 1/2 inch wider than the stock 7.5 i took out. MY PROBLEM is that the upper control arms do not line up properly. i did not remove them from the body for the swap, but the mounts on top of the pumpkin are wider and the holes dont line up. i dont think adjustable uppers will work because it looks like they need to be cocked about 15 degrees. to line up. racing seasons getting under way here in a bit and this is my last setback. I ran this car for 2 yrs (street) with a butcher job i did, by finally getting ticked off and hammering the arms onto the rearend mounts and redrilling the bolt holes. i want this to be Right this year . please help

I'm not sure about the compatibility of that rear, I assume you did you're homework on this swap and know somebody who has been able to make it work. I know when you are putting the rear back in it's not unusual for the arms to not line up when the rear is sitting on the jack much lower that it normally sits. You need to manuver the rear until you get it close to the right geometry and even then you might need to pursuade the arms to go on.

73 up mid size and big car 8.5 difs have different upper arm mount angles. The best way to correct the problem is to obtain the correct diff 64-72 a-body. 64-67 are slightly shorter. The other way is to make a pair of offset uppers.

Thanks Dan. I did jack up the rear until the frame came off the jack stand to achieve near ride height. im gonna fabricate something myself pretty heavy duty in the near future.