if you are building to the PA MINI PROS rules you need to stay with the 196cc clone, or a handa gx200. as for the best.......they are all about the same. most of the time you are replacing the stock parts anyway. if you are just starting into the mini pro class build,i would go with a bsp,or a ducar. these come with out the goveners and low oil junk to start with. there are also a ton of karting companys out there that can build a killer motor for you!