Glad you have some leads on SBP 10" drums. 'Cause IMO, a can of worms would be opened if 7¼ backing plates were used on an 8.75 axle. IIRC, the 7¼ backing plate mounts with four bolts, the 8.75 uses five. Then one has to be concerned about offset of the backing plate relative to the axle hub. (This is why a 7¼ can't be upgraded from SBP by stuffing BBP shafts in it.)
