1973 Dart Swinger cooling

Temperature sending units are definitely a resistance type meter. Generally the sending unit is matched to the gauge. It's reading it's resistance. When you put in a new sending unit you could have merely change the amount of resistance and make the meter read a different number. I guess what I'm saying is putting a new sending unit in doesn't cool your engine down it just gives a different reading. Aim the heat gun at the driver side head and right underneath the valve cover when the heat is at its hottest. If it says anything under 210 you're fine.... Obviously don't point it at the exhaust it will be well over three hundred....