Its quite common for the ignition switch to cause issues like you describe, the internal contacts get corroded from being parked outside for 30 years. I often pull the switch out, fill it with WD40, rotate it through all its positions several times and then blow it out with an airhose before reinstalling it. Fixed dozens of them like that.
The factory wiring really is the simplest way to go, anything else you may do can and often will create further problems in the future, people have burned up entire tractors... you dont want to be that guy
