4 wheel disc question

I would run the fronts direct off the master cylinder and put an adjustable prop valve in the front-to-rear line. I actually did that on my Valiant when I put K-H discs on it. Rather than look around for a factory prop valve, I just used an old-stock MP adjustable I'd picked up sometime in the past. Just make sure you adjust the valve correctly, preferably on a wet road just in case. Too much rear bias can have you looking at where you already were in a hurry.