No idea on the bearing, I doubt it since the tubes are smaller. The axles don’t interchange, just the backing plates.
As for the flange bolts, the 7.25 only had 4. But the backing plates usually had 5 holes, and the 4 are the same. If a backing plate is missing the 5th hole it can just be drilled.
You can use BBP 7.25” backing plates on a BBP axle 8 3/4. Had a BBP 7.25” in my Duster before I swapped to the B-body BBP 8 3/4. The brakes are the same.
