How would you get a lawn mower engine to power a soap box car from the back end. Im making a soap box car with a small lawn mower and I really dont know how.So can you help me?

Horitonal or Vertical Output? Horsepower? Keyed with 1/2 moon or full slot shaft? Gear or v-drive system? to comparable ability to transfer power to wheel drive system.verticle.6.5. full slot shaft and gear its a push lawn mower