I have a 51 6400. right now im getting it running and going it has the hydravac on it and a rebuilt master that i know is good i dont know about the booster. if its good im gonna leave it for now. but if its not then im gonna be looking for alternatives. what im thinking is what booster w/dual master combo can i go to cause i have drum/drum brakes. im gonna be hauling some heavy load and when i want to stop i want to be able to. can i get a m/c and booster from my auto parts place if so what model car would be a good one to use. otherwise which aftermarket one would be good. i have a 261 w/4spd. thanks chris