I have a 60 Bel Air that I know I am going to want to set up with a posi soon. It is going to have a mild 454 with a standard trans. The original car was a 6 cylinder and there is no "P" on the third member, so I am assuming its not a posi.

I have been shopping for a "drop out" that I could easily swap, but they seem pretty scarce, so now I am looking at getting into the guts of the rear end instead. I have a few questions about early GM rear ends such as mine...

How many splines are in an axle such as mine? 28, 30?

What size is the unit? 7 1/2 or 7 5/8 or other?

How many bolts? 10 or 12?

Anything else I should be aware of when shopping for a posi unit for my rear end? I do know I have to modify (grind) my housing to accomodate a posi unit.