Proportioning valve for rear discs

I put 4 wheel disk on a 56 Ford Pickup.

The fronts were single piston (don't recall the size) Granada? maybe.

Rears were Versailles rear with built in e brake, (such a great setup,)

I added an adjustable valve and had to set it almost all the way tight., (10 to 1) to keep the rear from locking up.

Rear tires were 295 50 15

Fronts were 255 50 15

The factory valve on our a bodies will be a good place to start, if you need anything else adjustable is the ticket.

If you can size the fronts and rears great, but typically the options are limited to what's available.