10 inch rear drum brakes

There are no 10 x 2.5 SBP backing plates. Original A-Body SBP rear 10 in brakes are 10.75. Original 73 up BBP 10 in A-Body rear brakes are 2.5. The backing plates are different than the SBP backing plates. But the 10 x 2.5 brakes came on most other platforms including PU Trucks.