Personally, I'd build a simple ladder chassis out of box section and take the steering from something like a go kart. Don't bother with suspension and stick a 12v motor in powered by a car battery. Then you can charge the battery with a normal charger. Get the pedal from a golf cart then it should have the variable speed you need. Then it's just a case of making a body, which will probably be the hard part.
or do everything you said except use a moped engine and autobox... makes it more fun
hi guys did any of you go for the toylander? just wondered how you got on and what problems you encountered??