Yeah there are several different Mopar drums. A-body drums are generally 1.75" wide. E bodies came with 2" and 2-1/2" wide brakes. B-bodies came with 2", 2-1/2", and 3" wide brakes. Same for trucks. Yours could be a simple drum mismatch or a complete hodgepodge of parts.
Is it small or large bolt pattern?
Just noticed you said the drums rub the backing plates. That's a sure sign the drums are too wide.
