I'm sure the performance parts would be interchangeable with a gx390. They make it 420cc by interesting bore x stroke, so most other parts should be interchangeable. I don't know how they would make money selling a 16hp engine with electric start at 189.99 and free shipping........ wtf? The 6.5hp looks cheaply made, but I have never even heard about these engines just stumbled upon them while browsing ebay. After I sell a few more items on ebay I'm going to purchase one. Hell you could even resell them for 225-250 on craigslist they would probably sell quick too.