Disc Brake Master Swap & P valve Question

I went from 9" drums all the way around to the 73+ 11" A-body disks on the front and 10x2.5" drums on the back. I used the proportioning valve from the 73 and swapped it in place of the distribution block that was on the car.

Whether other folks have gotten away with it or not I would plan to use a proportioning valve on the rear's. Drum brakes are self energizing and will lock up with a lot less pressure than disks will.

BTW, you never mentioned that you were swapping the upper control arms and spindles. You will need to do that to use the 73 brake rotor and caliper.