tamiya gear boxes?

[FlyingBeagle]

I personally dont have any experience with them, but I know that they are used fairly commonly in Bruder dozer and skid steer conversions. As cheap as they are it cant hurt to try one out and if it fails try something else. You may read in some of the bruder conversion threads and see what others that used them have to say about them.

[BOBCAT]

Sounds like a plan.
You need to change the motors though for some 12v scalextric ones, the standard ones are only rated for 3v i think.