[Cartwheels]

Definitely sounds like the fan clutch may have failed. do you hear the fan kick on high when the temperature rises? Use a large piece of cardboard and push gently against fan while running, the fan should not stop without a decent amount of force being applied. If you do end up needing a new fan clutch make sure you get a Mopar OEM, DO NOT cheap out with something from an auto parts store, it will leave u cooking over beside the road sometime

 

[Cartwheels]

Ok likely the viscous part is still working if it doesn't stop easily with cardboard. Could possibly be a wiring issue if it's not kicking on high.
I think there is likely another issue because it should not get over 200 when running empty unless it's an extremely hot day driving up a steep hill.
I guess the water pump might be the next thing to check.

 

[Cartwheels]

Did you use a Cummins t-stat??

 

[Cartwheels]

Geno's garage should have it.