10" rear backing plates??

Hey guys,,, I don't get it? I have a small bolt pattern 8 3/4 rear end. 10" drums fit the backing plate that came with it. drums are from the 7 1/4 rear end I took out of it. Problem is not sure what the backing plate is off? Have purchased 2" and 1 3\4" shoes, neither fit? Backing plates have 1 hole for emergency brake cable,,, so left and right. Inside of my 10" drum is a total width of 2 1/4",,, so 2 1/2" shoes are a No go. what is not correct with this installment?
Thanks for your time!