I do not have enough heat in my 1994 dodge ram truck

I expect the thermostate is stuck partially open not allowing the engine to come to proper temperature. Replace the thermostate found under the goose-neck (follow the upper hose back to the engine) under this piece is the thermostate. Be certain to clean all of the old gasket material away and use a new gasket. Watch to be ceratin the thermostate is not put in upside down, if this happens your issue won't be not enough heat but over heating.
I hope this may have been of help,
Tom