Hy Village_Idiot, if you purchase a master cylinder that is designed for a drum/drum application it will have residual pressure valves built into it, so no others should be required. As to the metering/proportioning valve, I'm not sure if one designed for a drum drum system exists. Because a pickup is usually so light in the rear end, rear wheel lockup can be experienced. My advice would be to install the system, and if you feel you're experiencing too much rear wheel lockup, I would install an adjustable proportioning valve in the rear brake line. Of course if you can find a metering/proportioning valve for a drum/drum system then I would install it. The supplier you purchase your brake system components from "should" have some technical expertise, so take advantage of it and ask for their opinions on your installation, hope that helps.
