I have a 1996 dodge ram 1500 and the heat hand with go all the way up to 260 as soon as you start it, well last night we were at the store putting gas in it and when I put it in gear it cut off. What could make it do that. It has a new thermostat, heat sensor, water pump, and all. What else could it be.

Dodge may have an interlock that cuts the engine off when it starts to seriously overheat, in order to protect the aluminum head. I had a new Opel Capri that I found out had that feature in heavy rush hour traffic in Geneoa, Italy. The car suddenly died on a hill--I thought the Italians were going to kill me. When the car cooled down over night, it started and ran flawlessly the next day.

This link may help:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-3.html#post235973

Inspect the radiator for phosphate scale and corrosion--it may need to be replaced.