No Electrical working
It HAS to be right there in the immediate power distro. Battery, battery clamps, cables, connections, the bulkhead connector, fuse link, or ammeter connections, in that circuit. DO YOU HAVE a factory service manual and or aftermarket/ 3rd party wiring diagram? Go over to MyMopar.com, they are free
Also look over this article which covers this part of the wiring. I am NOT advocating you modify it at this time, but the simplified diagram there is helpful
http://www.madelectrical.com/electricaltech/amp-gauges.shtml
Power comes to the "big stud" on the starter relay which is also used as a junction. Goes from there through the fuse link, through the bulkhead connector on "big RED" and to the ammeter. Through the ammeter, out on the big black and a few inches to the factory welded splice (These do break, but rarely, just keep in the back of your mind). At the welded splice, power is routed to the hot buss of the fuse panel, the ignition switch, and the headlights power, couple of other points depending on year.