Well I've built several of the Gen 3 ones, without the wings. But I have a Suburban cart here that almost the same thing , just bigger. You have to start with the correct frame, and get the tongue length correct, so that it will work with the hitch. There's nothing wrong with a gen 3 hitch, other than its more complex than the Gen2 hitch. If I get some time this weekend i'll put together some measurements for the frame and the box. I assume you having welding equipment? ,,,,, a drill press, and shop tools?. This is no project for the weak, lots of parts in one of these cart frames and the box. I'll post some pictures of the hitches and you'll get the idea of how they work with the tractor.
What part of MI are you from, I make trips up that way every once in a while.