Hy E.C. RatRods, If your vehicle has a combination of disc and drum brakes, then yes it most definately matters where the primary (closest to the brake pedal)system is plumbed, and the secondary system is plumbed. One of the functions of the proportioning valve is to limit pressure to the drum brake system to prevent drum brake lockup. I would recommend following the plumbing schematic of a vehicle that uses the components you will be using in your brake system, hope that helps.
