REV J completed a motorized drift trike build with 420cc Predator Engine. He utilized a rear axle kit from BMI Karts. Featured in video #6. This video is very informative on how to mount the tires and rims.
REVJ details every step of the build in series of videos on his YouTube channel. They start with a Mongoose Fat Tire Bike, add a tube notcher and bender, Predator engine and drift trike kit and the final assembly is a sweet but powerful motorized drift trike.