Wiring upgrades and ammeter operation
You could do this, you will have to play with wire size. The PROBLEM you will run into, is that if you do not bypass the original bulkhead connector terminals FOR THE AMMETER you will in effect still have part of the original problem
In effect, what you are doing ---on a different scale---is exactly what GM /F/ Mopar did when they all finally went to "remote shunt" ammeters...........that is,..........they all used THE HARNESS ITSELF for the ammeter shunt
The DIFFERENCE is that instead of using an ammeter for the dash instrument, they went to a sensitive meter, a milliameter if you will.
Now the Ferds were far from perfect. One of my (87) Ford Rangers was "so numb" that you had to stare intently at the ammeter when you turned the headlights on and off to see if the damn meter moved!!!
I once "more sensitized" an ammeter on a "Friend's Ford." I dug into the harness, figured out where the "ammeter" wires spliced in (small wires for the remote meter) and ADDED a length of no10 or 12 wire to make the shunt less effective, and force more through the instrument