Air in coolant system 97 Dodge Truck

Recheck the thermostat if okay go here:https://www.2carpros.com/articles/how-to-replace-a-car-radiator

First of all, make sure the belt was routed correctly. Because if not, it will cause the water pump to rotate in the wrong direction, and you'll get the same exact problems you are experiencing now.

If it is correct, then make sure you have the heat set on high, your heater control valve is opening and squeeze the upper radiator hose a few times with the reservoir cap off until all the air leaves the system