[SLESTAK75]

What kind of terrain will you be riding on and what do you want your buggy to do? It is a good idea to stick with the gy6 for ease of install. They are not all created equal though. There are some on here who are way more qualified than I to give recommendations. You can actually get a very impressive amount of power from these little 150s. There are bib bore kits, stroker cranks, forged pistons, as well as machine work to the head and intake, custom exhaust, and more. It all depends on what you want to do and how far you want to go. There are some engines out there that can be bought already built. Again there are others here who are more suited than me to give recommendations. Stick around, ask questions, if you take your time and do it right from the start you will be much more happy in the end.