Somebody above probably already said this. 580 K was available in many configurations. For example an open ROPS had a different group of harnesses from a cab tractor.
Once you have the correct set of schematics for your tractor, draw a partial schematic featuring only the portion of the harness affecting the issue you are having.
You are now better prepared to test what works, what doesn't.
In my experience, a new harness is staggeringly expensive. I ran new wires to replace the non functional portion.
580K (I have owned two) has four sections to the wiring harness. There are many mated plugs to combine them into a whole wiring harness. Most often the problems were failed connections in these mated plugs. I never found a source for the individual metal terminals to put in these plugs. I bypassed the bad connections.