I'd buy parts on eBay for a 180 swap. I can't imagine that the transmission would suffer, since the CVT is quite hearty. The carb will likely just need larger jets.
I've never done the swap, so I don't know any of this for sure. You can learn a lot from this site:
http://www.scrappydogscooters.com/12...OKE_PARTS.html
If you rebuild your GY6, please take pics and share them.