What kind of Master Cylinder would I use? 4 wheel disc

I am in the process of installing a Master Power four wheel disc brake kit as we speak. It came with a rebuilt master cyl similar to what came stock on BBP A bodies. Modifications have to be made to the stock proportioning valve (basically gutting it) which turns it into a distribution block. We are going to add an adjustable proportioning valve on the left rear frame rail so that we can make adjustments as necessary.