Overheating

[Mopar]

Your heater core is clogged if your not getting heat in the cabin which could cause the overheating.

I would still test for exhaust gas in the cooling system.

Not necessarily. An air bubble in the system will also keep heated water out of the heater core. Shutting off water to the heater core will not cause overheating. The OP had recent work done on his cooling system which increases the likelihood that there is air in the cooling system.

 

[Electric Banana]

I don't think the heater core is blocked. I will get heat in the cabin until it runs hot, then no heat. This is driving, when sitting the temp will slowly return to operating temperature and heat will return. I'm going to drain the system, change the thermostat and start with fresh coolant. I'll get the front end up with ramps and possibly get the spill proof funnel to get the fluid even higher.