ok,i thought this all started with a smog pump? anyway if youve got coolant lines,why not grab like a small oil cooler or smething and just hook it up? you don't really need a pump,convection will somewhat take care of that,and that way it will at least help. Your mower will run hotter but youll also be moving faster(i hope) run a bit of a ram air to the cooling fins,or through the fan and this will help a bit.