8 3/4 backing plates onto a small bolt with upgraded big bolt shafts

Ok here are some pictures of what I just bought. The guy said they were 11 x 3 but I think they are 12 x 3

For reference the wheel cylinder part number is Bendix 2227383

The only number I could get off the shoes was 323173

Pictures to follow.
Wasn't exactly sure where to measure the backing plates.
Apologies for the picture of the front of the backing plate I was trying to line it up with the groove that goes around the plate. The back side rear s measured more accurately it is from outside to outside

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