I have a 65 Dart with a 273 that I have been driving since last summer with a 71/4 rear end and not had any problems with brakes. This year I installed an 8 3/4 and now I cant get rear brakes to quit locking up, its almost like the front brakes are not working at all
Change out your rear wheel cylinders, get a set of 7/8 inch brake cylinders. Might also try an adjustable proportioning valve installed in the line going to the rear brakes.
so you got 10's on the rear and 9's on the front. Youll need to do some proportioning or juggle the brake cylinder sizes.