I found a 10 bolt posi out of a 76 Buick Riviera. I have a 71 Cutlass with a 10 bolt open. Will the buick posi fit in my olds?

 

Offhand I'll say no. The Riviera is a full-size and is probably wider than A-body. I was set to put a 3.42 out of a 73 Riv GS under my old 73 Delta ragtop until a deer whacked the quarter panel hard enough to spring the top frame. It was supposedly a bolt-in.

 

If I remember correctly the Riv used some wierd 3 trailing arm system unique to it.
I'm not sure if it is a standard 8.5 carrier or not though.

 

Instead of using the whole rear end can I swap out the guts and install in my housing? I don't know the size of mine yet.. 7.5/8.5? Or the spline differences.. My rear axle assembly has been blasted and painted and is still sitting at the shop and I haven't identified what I have exactly yet. Or should I just go with an aftermarket..?

 

I doubt it. If that Riv is a '76, it should be 455-powered. You'll probably find it's got a 8-7/8" Pontiac rear. Have you opened it? If there's 12 bolts on the ring gear, it's a Pontiac and nothing interchanges with the 8.5" rearend in your '71 Cutlass.
Now if the Riveria is actually a '77, it would likely have a 350 Buick or 403 Olds engine. In that case it should have the 8.5" 10-bolt.
The 76 and 77 Rivs are completely different chassis. The 77-up cars were based on the B-body. Make sure of what you have. We can help you if you post pics.

 

It is a 76 with the 8-7/8... darn. Well thanks for the help anyway! The search continues..