Steering wheel stops tractor from stalling?

My advise, take it with a grain of salt, but crank the engine, carefully push and pull on any wires you can get your hands on. Since the seat safety switch is disabled, this should be pretty simple. Of course, be careful not to touch any rotating parts.

I'm thinking there's a slight short in there somewhere.

I had this problem on one of those old green ones. Tested wires for hours. Always had continuity. But it would still cut out like that. So, I just swapped the harness (all of it) and problem solved.
I still don't know where the short was. I didn't even want to know, at that point. Just glad it was fixed.