Aren't those 3/8 N.P.T.????.....If memory serves me correctly they are the same as the cyl. head temp sender...(just checked an early 292 with threaded heater connection and it is 3/8 N.P.T.)...
To clarify... the fitting I'm trying to size the threads on is the LARGE one just to the passenger side of the water neck on the water housing. Since that heater hose is either 5/8" or 3/4", the threads are going to be much larger than 3/8"
