Here's an old thread, but the meter used "may not" be available. However this thread should give you lots of ideas. Please look through the entire thread, as it covers a lot of ground
Ammeter to Voltmeter...who does it?
The problems with the "full current" ammeter these girls use is several:
1...The bulkhead connector terminals were never intended for that much current. I used to perform HVAC/R service, and part of that was heat pumps/ electric furnaces. They use similar terminals in the heating element wiring. Those DO fail, and they only draw about 20-25A per heater element
2...The ammeter itself can become loose, build heat, and further destroy itself
3...The wiring is no where near large enough for 55+ amp alternators
Along about 70-72, "Ma" started equipping stuff like the C barges with "external shunt" ammeters, which are fed with small wire. The problem with these in Ford / GM/ Chrysler is that they can often be "numb" meaning they do not respond to "small" loads like headlights