Do the wipers work? If not, it's a fusible link for sure.
The fan works?
That runs off the same link....... Check fuses with a test light, see if all have power. Some have constant, some keyed.
Man, this is strange. I reread the whole thread, and stuff gets power from 2 different sources, but you get power on some and not others.
Did you try cleaning the battery terminals good? and any plugs in the large red wires to the fender stuff? Try that next, it sounds like a bad connection more than a bad link.
Good Luck!