Brake booster and master cylinder assembly

Steve, i am putting 4 wheel disc on my sons 69 cuda. Cordoba big brakes on the front explorer rear discs on the back. Your recommending to stick with a 4 wheel drum proportioning valve? I am curious, can you explain why? Reason I ask was I was planning on using a GM type 4 wheel disc proportioning valve that mounts below the master cylinder, and just bend, flare, and run my own lines. You sir have more experience than i do with the 4 wheel disc stuff. This is my first foray into it.