On my '72 Cutlass project I have a Olds 12 bolt rearend and I just aquired a 10 bolt off of a '72 Cutlass 442 (350)...both rearends are non-posi...are there any real differences between these combinations?

 

I found my answer in a previous post...forgot to search first.
...I guess I'll use the rearend that looks cleaner.

 

Use the 10 bolt out of the '72. Its an 8.5' and posi carriers and parts are plentyful for them. The 12 bolt olds rear is very limited on posi parts and not as strong. JKaz

 

While I agree about the limited parts availability, why do you say that the Type O is not as strong as the corporate 8.5"? Both have an 8.5" ring gear held on with ten bolts. Both have the same 1.626" pinon shaft. The only difference is the Type O has 27 splines on the pinion and the corporate has 30.

 

There you go...you answer you own question....

The yoke also is much beefier on the corp 8.5 too.

there is more support around the u-joint cap compared to the u-bolt set-up on the olds 12 bolt (which basically is a pontiac 8.2 yoke)

All in all for the street flip a coin. Jim

You can however up grade the 8.5 to 30 spline a lot easier than you can up grade the strength on the 12 bolt 'o' rear too.