there are about a dozen different ways of measuring current and displaying it on a gauge we'd call an ammeter.

ONE of those is to measure the voltage drop across a known resistor to infer amperage. Mopar eventually went to that style but not during the musclecar years.

the one we are familiar with uses magnetic fields.

there is nothing inherently wrong with an ammeter, however is may work. But the implementation does matter. Chrysler never built to last 50+ years so it is not surprising things need attention over time. All electrical connections need to be clean and tight. If they are not then heat gets generated. the more current flowing through that connection the hotter it will get.

Care to guess where the highest current flow is? Not the ammeter if you said that, the starter. That said, the ammeter does routinely get large amounts of current flowing through it so if those connections are not clean and tight then you will have heat related damage, maybe even a fire. I don't like that the charging feed into and out of the passenger compartment goes thru relatively small packard connectors that are exposed to the element. Clean them, use dielectric grease to protect them.