proportioning valve

In '69 the drum brakes did not have proportioning valves, only combination valves that all the brake lines route to. The disc brake cars in '69 had a combination valve and were supposed to have a proportioning valve back by the fire wall on the frame rail. If you get reproduction rear brake line for a disc brake car it will be two pieces: one to go from combination valve to proportioning valve, and a longer one to go from proportioning valve all the to the rear axle flex hose.

Put some 7/8" wheel cylinders on the rear too to dampen that rear wheel lock up...