Baby's 1st Engine Swap: GY6 Fitment for '15?

Hey yall. I bought my 2015 Ruckus off Craigslist in 2016 pre-modded with a handful of things. Seller seemed kind of amateurish from the interaction. After 4 years and 4k miles, one day I suddenly found I had severely worn splines on the crankshaft, to the point where it wasn't driveable. It's been sitting for the last 4+ years. It only has like 7k miles, it's a shame.

So I'd like to do a GY6 swap. But I'm just now realizing how generic of an engine that is. I know I need long case and horizontal cylinder angle. Are there any other parameters I need to consider for the Ruckus specifically, when buying on Ebay?

I'm in Kalamazoo, in SW Michigan. I'm open to buying locally, for cash or trades. My husband and I do renovation work. I suppose I'm also open to any shops/hobbyists willing to do the install. But I've had a really hard time finding people interested in my project.