65 Valiant now gauges go full when ignition key turned or running

When I was doing all this mess. After it lost power after I turned on the headlight switch for the first time I was able to jiggle the negative battery cable around the terminal and hit a spot where I saw the dome light come on. I did my "re-test" by pulling the headlight switch on and the dome light went right back off. After that I could no longer find any "sweet spot" by wiggling the negative cable on the battery post. I'm going to try a new negative battery cable because I've been looking for an excuse to change this one because the terminal is so much fatter than the positive and it just doesn't look right. I don't think I've ever unbolted and looked at the ground wire from the firewall to the block. I think mine goes from the head to the blower motor nut. Where does the Slant Six negative cable bolt to for ground? I've got mine bolted to the bottom of the block right under where the power steering pump would be. I don't remember if I mentioned it but after all that happened I checked for power at the alternator stud, relay stud, and the ammeter studs inside and there was nothing. It's either lost ground or fusible link has gone but I don't know how. Because everything always powered up as soon as I connect the negative cable. There was no burning smell or smoke so that's good news. I'll check it all out again the next day I'm off.