What 8 3/4?
An "A" body 8 3/4 will be 4 inch SBP and the small drum center hole. The 7 1/4 BBP 10 inch drums will be 4 1/2 inch BBP and large center hole.
The BBP 7 1/4 backing plates do have 5 holes and I think they are the same pattern as the "A" body 8 3/4 (I don't have a 8 3/4 backing plate that I can measure). I do have small and large bolt patten 9 and 10 inch parts I can measure.
