8 3/4 Backing plates SBP question

News to me... A few years ago I was assured the 7 1/4 10x1-3/4 brakes were a direct swap to an 8 3/4.

I believe most of the 10X1.75 parts...shoes, drums, wheel cyls, etc. are interchangeable EXCEPT the backing plates are not.

72 back small bolt 7.25 plate left , large bolt 10"x2-1/2" right (same flange as 8.75)


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8.75 shim laid over 72-back 7.25 10" x 1.75" backing plate.
flange stud holes dont line up and center is much smaller.

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