Is this an 8 3/4 ?

mbaird said
Guy says it is a 50s rear end ?

Banjo type rear ends were introduced in '57. That should interchange just fine. I believe there was some thrust block variations in non suregrip units prior to 64. This is probably from one of the early units that had tapered axles.

Carrier casting numbers: 1820657 (1957-1964)