Was a 10 bolt rear end available as an option in 1970? I've found several Rallye 350 cars that have a 10 bolt rear end.

 

The Olds O axle had a 10 bolt cover, bolt in axles (no c-clip) and 12 bolts holding the ring gear yo the carrier. The 8.5 corporate axle also has 10 bolts, uses c-clips, has 10 ring gear bolts, and was used from 1970 (I think) up until the rear wheel drive B body ended production. There are many on here with more knowledge about the different axles used, I provided the limited knowledge I have on them.

 

The "O" axles have 10 bolts for the carrier-to-ring connection, not 12.

 

The O-Type has a 12 bolt cover and a 10 bolt ring gear. These were used from late 1966 up to 1970 on most all Cutlass models.

The Olds manufactured 10 bolt rears were introduced in 1971. These do not have c-clips, they have bolt-in axle shafts. At some point the change was made to c-clip style, but I do not know when that happened - possibly late 70s? I had a 10 bolt rear out of a 1975 Cutlass that had bolt in shafts and I think my Mom's 1978 Delta 88 had c-clip shafts.

Anyway, for 1970 there may have been some models that used the 8.2" 10 bolt rear.

 

I'm afraid you have that backwards.

 

LOL he is describing a 65-70 B Body Pontiac rear

 

Its up to the reader to interpret what I meant to say, not what I actually typed. 😎😉