cooling problems

i have a 1996 aurora that is running hot 250-270 but no hot air out of the heater? blower blows hard but no hot air comes out, just cold air. thermostat? i've already tried 3 different brands? new water pump also.

With the fact that you have done work on the water pump I would check if you have an air lock in the heater pipes. Other that that, there may be a problem in the blend box under the dash. If one of the actuators is not working then the door it controls will not open and allow hot air movement.