The Magnum V8 temp sensor is a thermistor and will falsely read high temperature if the wires short and resistance is low.
If my memory is right 212F degrees is about 640 ohms. The Ram FSM has a table of ohms versus temperature.

The Magnum V8 factory thermostat is a
Sieb/Robertshaw standard grade with steel body and brass underarms.
The brass will crack,
which will cause the thermostat valve to cock sideways to fail in the mostly closed position.

If you have to work on these
take out the 10 extra bolts
and lift the alternator and AC compressor off to the passenger side
so you can work on them properly.
Permatex "Right Stuff" made a good gasket-less seal on the thermpstat housing and teflon tape made leak free seals on the thermistor sensor.