If its a stock A body 8.75, it is guaranteed to be small bolt pattern. When Mopar changed the A Bodies to the 8.25 integral axle is when they also changed to BB pattern.
You are probably right, I have two BBP 8 3/4 in shop but they were probably converted, one has non stock axles. Other might be redrilled, but now that I think about it, I have never pulled the hubcap off....front is BBP but....selling 8 3/4 rear disk kits in BBP throws me off :D
are all 7 1/4 SBP? I know not all /6 are SBP, my 74 sport /6 has BBP 8 1/4