What do I need for a proper under-dash rewire?

If it had a map light it likely had the lighting group which included a delay timer on the dome lamp circuit. You might find a tiny light bulb above the ignition switch bezel too. When that delay timer would fail, the owner might hack a lot of stuff trying to end the dome lamp always on and battery kill. Sure I'm only guessing why the wiring was hacked but there had to be some reason for it.
So.. repair the conductors per the diagrams. Once every component is properly connected and chassis grounded then you find which components need replaced.
I'll add that if it were mine, I would totally delete that lighting group. I do use the basics, a glove box lamp or the trunk lamp, but I don't need the dome lamp to remain on while I dig my keys from my purse. Nor do I plan to spread a Rand-McNally road map on the passengers seat and floor.
I can't honestly speak to the lighted key switch issue. Mine is in a chromed bezel. Maybe the 68 model key hole is more difficult to see/ring under that odd shaped color keyed bezel. My total delete plan would delete that lamp too. Anyway, Good luck with it.