These are often available on the bay, made by ZEE (SPRINT BANDITS) and Road Champs... They are die-cast... There was a thread some time ago with information on converting them to slots.
Here are a few I have and a converted unit also. It`s up to the builder how you go about it. But they do run surprisingly well.
wheelbase is 2-1/4" overall length at around 4-1/2"
