Chrysler Corp's L-head engines incorpoated formed sheetmetal tubes to direct coolant from the output of the waterpump to each cylinder. These "water distrubution tubes" were originally made of galvanized steel and of course rust-out over time which leads to engine overheating. We offer a distribution tube kit on ebay which also includes new core (freeze) plugs. Frequently we are asked if we can supply the replacement tube and core plugs in brass. The answer is no because since the engine block is made of a ferrous metal (iron), everything in contact with the iron block and the coolant water should also be made of an iron-based metal. If  you remenber your high school chemistry class, you leaned that if you immerse two dis-similar metals (iron and brass) in an electrolyte (the coolant water), you will have created a galvanic battery cell that will rapidly erode the least "noble" metal part (your engine bock). You don't want that! Making sure that any metal parts used in the cooling passages are made of a ferrous (iron-based) metal will keep the erosion to a minimum. Because of this, you probably won't find a brass water distrubution tube but there are mechanics that will try to install brass core plugs into your engine's water jacket. Don't let them!