What do you plan on doing with this mill? You say you build race cars, well most car components you would need a mill to make or modify are about the size and weight of that thing... I would look for something along the lines of a g0704 or x3. also, it sounds like you intend to use the cnc to just jog the axes around, in which case it would basically be a manual mill for someone who is really lazy. It would have basically none of the benefits of CNC.
Soooo....what do you actually want to do with it?