Hy JRMunn, I have never seen a truck with two hoses to supply the rear brakes, but the trucks I know best were built a decade before your truck. The systems I am used to seeing have one hose from the chassis to the top of the differential where there is a tee fitting from which one brake line travels down the rear axle tube to the wheel cylinder connection on either side of the truck. As I said there are older trucks with the system I have described and they have multiple wheel cylinders per side, of the same capacity as yours and the rear axle flexible lines that we are discussing have more than enough capacity to supply to supply those wheel cylinders, hope that helps.
