Help it is grinding bad

:banghead::banghead::banghead::banghead:I just put in an 8 3/4 out of a 66 charger it had no backing plates I picked up some 11 inch drums and backing plates. When I went to buy shoes they were 11x2 shoes. The local parts store showed them to be for a Polara. I installed axels with
green bearings put the drums on went to test it out and the drums are rubbing badly on the backing plate. I do not know what to do. Why is it rubbing in there. The drums and backing plate came together. :oops:This has been ridiculous I have jacked with for weeks.