Swapped the Pushrod back to stock location. The pedal came back firm.

Went for a first ride with the prop/combo valve installed. This si the prop valve for a 70 the has 2 parts. I only used the lower part that is similar to drum brake distribution block.

Took the car for a test and found the prop/combo valve makes a difference. Backs don't lock regardless of existing "adjustable prop valve" position.
Actually, the fronts work better with the adjustable letting more fluid to rear since it cuts them off quicker.

I would consider that braking is now good. I will move to 7/8 rear wheel cylinders and hope for continued improvement.

Do you think that 2.75 Diplomat Calipers will help the cause???

Thanks