E-brake cables same 7 1/4 to 8 3/4??

Most likely. The distance to the center of the axle has not changed. You can usually use the box end of a 9/16 wrench to slide up on the retainer of the cables in the backing plate and get them to release if you wiggle the wrench a little. Most of the brake hardware is interchangeable on 10" brakes on up into the 80s and beyond.