vinny,speedway motors have single 12v motor & arm kits for 49.95 and a duel setup that uses a single motor and a screw type system for duel arms, but it is 399.99 ! I got the duel system at a swapmeet for super cheap in a big box of other parts, so I'm going to use that drive in my humpback project. don't know if this helps you or not. just throwing it out there as an alternative.