think you will need the proper residual valve for the drum brakes along with the prop valve---the residual is set at about 12" column pressure---this keeps your shoes in close proximity to the drums so that you dont have to pump up your brakes everytime you stop----if you look at a hot rod buildup in a speedway catalog you will see you need 2" column pressure on the front discs-------so if you have a rod with a frame mounted master--you have to have a residual for the front(2") and rear(12")----however if you have a firewall mounted master there is sufficient column pressure for discs but not for the drums hence you need the residual valve and that is the forgotten value of the distribution valve...