So, here’s the scoop, the 8 3/4” backing plates have 5 bolts to mount to the housing, the 7 1/4”only has 4. There has been word that you can drill the 5th hole and use 7 1/4” backing plates, I don’t believe that’s possible. That assumes that the other 4 bolt holes are in the correct location. However, 10x1 3/4” brakes will swap to 7 1/4” from 8 3/4” if you have 10” backing plates from a 7 1/4”, even the drums and hardware are the same.
