The BBP axles from the 8.25” won’t fit the 8 3/4.
If you bought BBP axles for the 8 3/4, then yes, the BBP brakes should fit. Assuming that the BBP A-body 8 3/4 axles you bought aren’t actually re-drilled SBP axles. Or moser axles made with the 5x4.5” pattern but the SBP axle flange offset, because you can buy those too.
The BBP brakes will fit as long as the axles have the BBP and the correct BBP flange offset.
