Go kart engine??

Ok so I'm thinking about building a drift trike (I have none to very little experience with things of this kind) I will have my dads help and probably some people that know more about things like this so what I am looking for is a engine I weigh 140 and am 5,5 and have not hit my big growth spurt so I want to get a engine that will last me as I get bigger but any way I don't want the thing to go crazy fast maybe like 30-35 mph top speed and I want the egine to be good quality not some piece of junk that will break in a year also I would like it to have ok mpg and not to be on the expensive side (I know this might be hard to find) like max price 300-350 so yea