67 Dart 383 high temperature question

My 383 gts temp gauge was running higher than normal so I grabbed the IR gun and measured the back of the water pump it was fine. I also took out the small hole thermostat that was installed in the engine after it was rebuilt and put back in the high flow design thermostat that had always been in the engine. I also changed out the voltage regulator for the gauges since they were suspect. I think it's the original sensor.

It was fine until lately when it runs 210 or sometimes 219 on warm days. Then the next day it's fine again or if I stop it and restart it after 10 minutes it will go from 220 to 209. Not sure what is going on here. 180 thermostat thats less than a year old. Funky thermostat maybe??

I've alwasy run a 180 stat and it would heat up some in warm weather when stopped in traffic but would cool back down when you got moving. I ordered a 160 figuring I dont' drive it in the winter so I don't need to worry about heat in the car with very cold air. Maybe 160 it a bad idea and I should try another thermostat.

So today I went to work in the Dart and it was fine going there. Left work and it was fine and made a stop for 10 minutes. After the stop it started indicating higher running temp probably around 219 didn't have my IR gun with me.