14 GA or 16 GA Fusible Link?

"The trouble" with external shunt ammeters generally and practically:

I've had some Ford Rangers, and friends with Chev and Ford pickups. ALL had external shunt ammeters, and ALL had the same problem:

They were "numb." That is, you could get in, turn on the headlights, and you had to stare intently at the ammeter to see if it even moved!!! Almost useless for smaller amperages. I actually added some wire to one Ford harness to "de-numb" the ammeter. All these, whether Chrysler, Ford, or GM, used part of the harness as "the shunt." This means they can never be very accurate, or repeatably "accurate." They are, in fact, a huge compromise

And that is likely, exactly, why most (all?) modern vehicle manufacturers went to VOLTMETERS They themselves are a problem, as the faces are simply not accurately or meaningfully calibrated in many cases.