I cannot thank Dan enough. What a guy.
He got a hold of me this morning, probably sensing that I was about to lose my bananas, and got me back on the right track. Loaded me up with knowledge, but, probably the best advice he had, "get an impeller and go use your damn boat this weekend." Well played sir.
After the impeller issue became blatantly obvious (previous owner thought it should be fine) I ran down to the mom and pop marina on the lake I was at. They didn't have one. Dan cross referenced the part numbers and gave me four options to go look for. I'm in Western Kansas, I have one real marina within 300 miles. Drove over there and picked it up, ran back, installed it, and magically my overheating problem is no more. Ran 140 for 2 hours straight (I don't think it has a functioning thermostat).
This allowed me to go out for my first actual run with this boat and made my weekend.
I still have a list of issues to address, but no new ones popped up while out boating. Thing runs like a champ. Little vibration, but nothing insane. Found out today that the strut bearing has never been replaced, go figure. With that same logic, I'm assuming it's never been aligned either. I figure once I handle those two things I'll be in real good shape. Trans still spins a little in neutral a bit, but I'm not going to over think it until I get the strut bearing swapped out.
Sorry for the novel, anyways, just wanted to publicly thank Dan for all his help.