There is a 3 speed motor I've offered free for the cost of shipping in the Swap Meet Freebies section. It is however 12v and if you are keeping your truck 6v it won't work but you could check the measurements if you're going 12v. Many of these motors used the same size casing, mounting bolt pattern, shaft diameter, etc and would swap out easily. You would need a 4 position switch...off, low, medium, high. Those are very easy to find.
