The wiring at the fuse box and main 40a fuse were corroded and caked in 41 years of dirt. I still couldn't get the engine to turn over from the driver's seat, so I set to replacing the fuse box and 40a fuse.
Original box
Those fuses look good, but are they really?
Old 40a fuse and replacement:
It's made for marine applications, so should be fine for tractoring