4 wheel disc master cylinder?

4 wheel discs on the 55 in my signature. Fronts are volare rotors and camaro / s10 calipers. Rear are ford explorer 8.8 discs. I use a volare manual master cylinder designed for disc / drum with an adjustable proportioning valve. It works fine. I have been told, and can confirm through experience, that new master cylinders no longer use the drum brake residual pressure valve. The setup works great.