Well, she's all back together, and still spinning, but, uh...we're going to call this one the practice engine. I was able to flatten out that spot with a little rat tail file, but it left a tiny hole going into the hole for the head stud. Not only that, but the magnet wasn't easily slipping onto the shaft, so like an absolute knuckle-dragger, I "installed" it with a deadblow hammer and a socket, and when the nut wouldn't start, I just cross-threaded it on. On top of that, after I did that, I saw the woodruff key had popped out of the shaft and landed on my workbench, but that's probably okay since I needed a deadblow hammer to get it on in the first place. So this motor's probably never coming apart ever again. Most likely, I'll spring for a built tuner engine at some point in the near future.