well, if you are talking track car where you just want to keep the mist off the inside of the windshield, pull it all out and get some rainex?
otherwise, if you don't need heat and just want to move air around, perhaps remove the heater matrix altogether and just tie the plastic ducts together with some flex hose and hook-up to a manual blower fan:
Allstar Performance ALL13010 Compact Inline Blower Fan 3" Diameter 5" Long | eBay