if no coolant circulated then it indeed did overheat or came close. I can't say your gauge was off because I wasn't three

 

The temp sensor is located in the cylinder head on the magnum no? It hit a Max of 210 at the end of the drive.

 

Temp sensor is located in the intake manifold front coolant crossover. Either by the heater hose barb on the passenger side, or, right next to the thermostat housing.

 

Update: ran a pressure test on the cooling system, held 15 psi for ten minutes and didnt budge. No sign of oil/coolant mix. Ran a compression test, no sign of a blown head gasket, but piston 6 seems a little low. Here are the results:
1 150
2 150
3 160
4 160
5 150
6 120 / 145 after squirt of oil / 160 after another squirt
7 150
8 170

​​​​​​Guessing the ring in cylinder 6 is worn, explains why I see a bit of white smoke in my exhaust sometimes. Was happening before this incident though. What do you guys think?

 

White smoke is water of some sort. Either coolant, or simply condensation. Blue is oil, grey is a rich condition. This time of year, a puff of white smoke doesn't disturb me much, as the air tends to be VERY wet anyway......

#6 is a bit low, and you test does indicate rings are on their way out..... The rest look good though, so, if you aren't having any performance problems, I would just run it.