Stumble on takeoff?

[OrrieG]

I believe that the proportioning valve does not care if it is boosted or regular pressure. If the existing manual mc has two lines to a proportioning valve that serve a drum/drum or disc/drum setup then you should be good. If you are changing from single without a proportioning valve, or from disc/drum to disc/disc just get a prop valve that matches the mc. All the prop valve does is make sure one end stays working when the other end fails but the internals are specific to the type of brake system.