Race Go Kart Help

Hello. I just bought this go-kart for $60 and the engine that came with it is a gc160. It is not mounted and I would like to put on a different engine. What engine should I use? I want a used race kart engine and where can I buy one. If someone wants to sell one ill buy it. How do I adjust steering as it is for oval track racing? What hub do I need for the wheels in pic #2? sorry for all the questions but if if you could help that would be awesome. Thanks