I'm running a original "puke tank" On a 46 that works fine with out a pressure cap. The old truck has ben run through the Ozark mountians reaching as much as 200 degrees and worked fine. Checking the coolent level each morning finding it about one inch below the filler cap. It has the original 46 cap with a new gasket . I've never seen the insides of the tank but I'm sure it's hollow with a over flow spout.
