Heater blows but never really get hot, also temp gauge cold.

Most heat problems (or lack of) is usually related to the heater core becoming clog. However I don't think this is the case with your car. Since the car is not running at proper temperatrure , I would suspect that the thermostat is stuck open or has been removed.

i also have this problem, i own an 82 150 and not only do i have problems with the heater not blowing hot enough, i think i have a major draft comming frome somewhere.
and my temp gauge never works either, but my odometer never does either.
i had my fan go out and now its directly wired to the battery and i noticed that my heater core doesnt stay warm for more than 20 seconds after i turn the key off.