You can bleed the master cylinder with a cheap kit. I got this style from Napa. This is how I do it. Just keep the lines submerged while bleeding. You can do it using your brake petal as well you just need someone pumping while you keep the lines in fluid.
Also are you just using a proportioning valve ? I would use a 1974 Disc brake distribution block then maybe a proportioning valve if needed. I am not sure but I don't think just a proportioning valve will work but I've never done it that way.
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