Are the parts interchangeable? Backing plates, etc. Are they all 8.5's?

You're going to need to pick a year first....

I think the 10-bolts are:

67-70 Camaro == 8.2" Chevy rear
67-70 'Bird == BOP 8.2" rear (?)

71-81 Camaro/'Bird == Corporate (Chevy) 8.5" rear

82+ Camaro/'Bird == Corporate 7.5" rear (?)

Pretty sure backing plates are interchangeable between all of these, but the rest of the bits, not so much.
Someone who actually knows what they are talking aboot will likely correct me.

you answered my question , thanks