From what I can tell, some of the extra wiring appears to be grounding mods, from the way they are screwed to the transformer panel.
Honestly, from the photos, it doesn't look that bad.
If the cement resistor attached to the bridge is screwed down directly to the metal of the transformer panel, that could be one problem right there. It needs to be screwed down to a plastic post, or it will create a short with the transformer panel and blow fuses.
If you can re-do some of the custom wiring, check things against the schematics, get a known good MPU in there (or repair the original), replace the screw-in bulb socket fixture with a florescent fixture, and I think it could live again.