7 1/4 to 8 3/4 rear end interchangeable parts

I have a 7 1/4" out of a 1972 Dart that has 10" brakes. I just went out and pulled off one of the drums and measured the brake shoe width. This one has 1 3/4" brakes. Everything looks just like the brakes on my 1969 Dart with 8 3/4 and 10" brakes. I can't say if the backing plate to axle housing connection dimension is exactly the same.