[Christ]

You could put a heater core in the intake box (if you still have a stock intake) and run tap lines from your original heater core into it. The control would be as simple as a cut-valve on a cable from any older car... (88-91 Honda Civic for sure has them) or you could make a simple flap in your air box that would still allow cooler air to bypass the heater core, so you can somewhat accurately control temperature.