Lights flicker and gauge jumps around???
Uh, after 46 years it's probably a good idea to get rid of some of the BAD ideas that the mfg'ers had for the new stuff. Ammeters were a bad idea fro the start. JMHO .
Actually, I don't agree. I actually prefer ammeters to voltmeters IF THEY ARE PROPERLY designed. "The big thing" (which Ma KNEW how to fix, by the way.....) was poor design of the overall circuit, not large enough terminals, and wire that is too small.
Ways around the problem.........
Ma could have used the "big" feedthroughs used in the early '60s for the ammeter through the firewall.
Ma could have upgraded the wire size, and improved construction of the "guts" of the ammeter
Ma DID part of this with what is known as "police fleet taxi" wiring, which feeds larger ammeter wires through the firewall separately
In the early 70's almost everyone.......Ford, Chrysler, and GM.......went to external shunt ammeters on 'some models' like the big sea barges. Friend of mine had a 70 Chev pu and it had an external shunt ammeter.