I'm putting together a 8-3/4 rear for the wife's '67 Cuda. It has the large bolt patten axles all ready, so that's a plus. It has 10 X 2-1/2 drums on it now. I have these mystery 11 inch backing plates. How wide of a shoe can I fit on it? Is it a matter of drum depth or is there a backing plate issue with the 11'inch drums?