Which master cylinder are you using? As far as the proportioning valve goes, I would just run an adjustable one for the rear. Most master cylinders are biased to the front, but with the disc in the rear you're going to have to "dial" out the rear a little more. In fact your rear discs will end up being a lot bigger than your fronts so you'll have to take out a lot of rear brake. Have Moser send you a Wilwood adjustable proportioning valve when they send the rear end. When you get it all together just dial it in til you have the balance you like. When you first try it the rears will probably lock up with out the car nosing over. As you dial out the rear the nose will start dropping before the rears start locking up.