Having owned a 1995 Pace Arrow, I know that the "carbon buildup" head removal is my first red flag. Whether it's the Ford or GM, most likely the Ford, it will run hot. The more likely issue was something else or he had a history of driving it hard with a lot of engine knock.
The tires, he may have overpaid but he had to buy eight of them since it's a tag axle rig and they are likely 19.5" wheels. You should have 16" wheels on your existing rig which are far easier to come by and much cheaper.
The ethanol free fuel is another red flag. Who would sit and wait and fight to reach the one pump of ethanol free fuel, then pay nearly an 80% premium for it so he can still get 7 miles per gallon? It doesn't pass my smell test. My biggest issue is finding a place I can get into for fuel, I certainly don't go looking for organic bio-diesel with fragrance added.
As mentioned, 50 amp is better than 30 amp. As for the gensets, you're comparing 63.5 to 68 amps of power. Not a huge deal if they are both burning gasoline. If either is an LP unit, that's a different story and they shouldn't be. I'd side on the low hours unit.
Everything else seems to be the devil you know versus the one you don't. I think that the world is full of deals like the 37 and I would wait, instead I would go out and enjoy your 33 footer, discover what you like about the lifestyle and then consider the entire broad range of choices if you still want to upgrade.