600cc or 636 Kawasaki 4 valve motors. I believe it’s 917cc for the older motors, we used to use the cb750 ohc engines. Direct drive no clutch gearbox etc. just like regular midget, sprint etc. 10 or 13” wheels. There is a max width the rear of car tire to tire. Don’t remember the wheelbase restrictions. Most use standard Schroeder steering or now the newer Bailey versions of the Schroeder they’re non power steering units.