I just replaced my 6V gauge with a 12v gauge because the guy that had the truck before me did the same thing, just installed the alternator and the resisistor at the coil. One side of the old gauge coils was fried black, the other side was black in the center. not to mention one of the leads was burnt open.

52 Chevy 3100 5 Window, LS Swap, 4spd Auto, Vintage Air AC / Heat, CPP Power Front Disc Brake Conversion with bearing upgrade, Power Steering Conversion, LED Tail Lights