Not entirely true. The axle flange offset is different between the 8 3/4” SBP axles and BBP axles. 10x2.5” drums only work with BBP axles. So yeah, the 10x2.5” drums can be used on any 8 3/4” housing, but they must be used with BBP axles. They won’t fit with the stock A-body SBP axles no matter what backing plate you use.
Can you shed some detail on "axle flange off set". My 68 Notch has 8 3/4 with skinny brakes. Diff has been shortened with aftermarket BBP axles. I want to ditch skinny brakes and switch to 2.5" everything. Thanks