Hey guys I plan on changing my gears and going posi in my 72 cutlass but I don’t know if I have a 8.5 or 8.2 rear end

 

That is a 1971-1972 8.5" 10 bolt rear from the Oldsmobile division. The block "O" on the front of the axle tube in your last picture is positive ID.

 

This was standard equipment in every 1971-72 Olds A-body car, and except for the axle shafts and bearings, the internal parts interchange with those of the same vintage 8.5" Chevy ten bolt axle. The axles are retained with plates at the outboard end, so there are no C-clips.

 

thanks i really appreciate the information