I have a 2001 Dodge Ram 1500 318 motor. My heat gage says 80 to 85. I changed the water pump, the thermostate and flushed the rad. But still only reads 80 to 85. Blows only mild heat. What else could be the problem

Back flush the heater core. I did my Ranger a few years ago and all kinds of gunk came out. Perfect after that.