"""slam it into park...!""

I've never seen Bjorn so agressive!!

You have cleared all other known issues (battery, main wires, starter, solenoid), so focus on the ignition switch or the nuetral safety switch.

I replace battery and starter every 12-18 months just to avoid having to trouble-shoot them on my bird. Cheap parts to replace and this allows one to FOCUS on those things you have not recently replaced. The ignition switch and or nuetral switch could be 38 years old!