Disc Brake Hold Off & Prop Valves

I rundisc fronts/ drum rears ,big rear tires and no proportioning at all, AND I upsized my rear wheel cylinders.
Point is, with the big and littles I run; 235/60-14s, and 295/50-15s, The car stops excellent, in any situation.
I had trouble with the factory dual-diaphragm when I installed a 292/292/.508 cam. I swapped to a newer Single unit off a 73 Swinger. Problem solved.