Their should be a way to make your idea actually functional. Might have to get a smaller but higher amp rated motor, but something should fit. As for making a varialble speed unit out of it all that would need to be done is a rehostat put in series with the motor and switch. A direct bolt in functional replacement would probably sell like hot cakes between the Nova, Camaro, Firebird, and Ventura guys. Might have to tear one apart and see what I can do with one of the metal fabricators at our shop.