Rear Brakes locking up

Bendix, used to offer a wheel cylinder rebuild kit for the 13/16 cylinders, might still be able to get a kit, might be a good idea so long as the cylinders you have now are not pitted. Some thing to think about.

I just did a quick number crunch, and the 15/16 wheel cylinders add just shy of 25% increase in piston area over the 13/16 wheel cylinder; about the only way to make the 15/16 inch cylinders work is going to be an adjustable proportioning valve on the rear brakes; OR try a set of 7/8 inch dia cylinders.

Good luck!!