The 10x1.75" backing plates are different than the 10x2.5" backing plates.
The backing plates I sent you are 10x2.5", I know this because they had 10x2.5" drums and shoes on them before I stripped them down to the plates. Those plates will work just fine with BBP axles, as long as they aren't re-drilled SBP axles.
Some of the later backing plates are slightly different from the earlier ones, the later ones only had one slot and only one of the parking brake cable holes was drilled, so there's a left and a right. That particular pair of backing plates came off of a late '80's Diplomat, so there may be some slight manufacturing differences from the '70's versions. They work just fine. :D
