You can either redrill the drums and axles or get custom axles and redrill the drums or you can get new drums. The 8 3/4 was only installed in the A body up to 1972. After that, they got the 8 1/4 if they were the large bolt pattern or the 7 1/4 with the small bot pattern. The 8 3/4 was dropped. It never had the small bolt pattern, so you must choose one of the above choices if you want to still use the 8 3/4.
