Alright, after almost two weeks, the forum is working for me again! Yay! In the meantime, I bought an eBay replacement motor. Kart is running great, drifting and doing donuts again! For anyway else looking at a GY6 swap, some things I learned:
Most of these engines are set up for scooters, not karts, so there are pins that are made to hold drum brakes around the drive shaft. They must be removed, and for the bottom one, that means tearing the gearcase down. Prolly gonna have to do that anyway to reuse your old drive shaft like I had to. Problem is the large hole left in the gearcase once you remove the pin bolted in (and oh yeah, they shipped it full of oil). Plan to fabricate a solution. Other than that, the new motor runs great, and I'm putting only rec fuel in to try to keep the carb healthy until I sell it.
Someone price check me on this . . . Link deleted.