Actually the fan sits under the horseshoe shaped heater and sucks the air down, so I am not sure if any kindof modern fan would work. I have a small one on my race car I will check to see if it might work. Are any dc motors capable of running different speeds? I think maybe yes.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.