PRC Conversion Radiator Fitting Size?

[sjaroslo]

I have an LS Conversion radiator for my 67 Camaro from Prodigy Customs; it looks like it is manufactured by PRC. There is a threaded fitting (female bung) just below the upper radiator connection that is for the steam vent connection from the engine--does anyone know what the thread is on this fitting? I've been away from the nitty-gritty of hardware for too long to be able to eyeball it.... Should one be able to assume that we're likely talking NPT here?



I can take some pics if that would help, but hoping that someone has the radiator and can remember. Thank you.