i have a master dual ,not the single...havent put it on yet but its for disc.I am going to change out 7 1/4 to a 8 1/4.But i live in san diego drive the freeways to work almost rearended someone today they stop fast i stop slow bad combo.break upgrade before i kill my car.i dont have prop valve.was wondering if i should buy one for the 79 diplomat or go with like the ssbc style prop valve..any suggestions on aftermarket prop ? thanx.:blob6:now i will buy the set up .thank you for answering my question..:wave: