I am not familiar with the earlier dash ammeters which ran full alternator current through the dashboard and back out.
An Ammeter is a wonderful tool, but without a voltmeter on is pretty blind. Same for just a voltmeter alone.
My 89's ammeter, I ripped it out long ago and replaced it with a tachometer.
I also have 2 voltmeters, one for each of my batteries.
You could likely get away with your system, as is, by using a battery charger when at home.
I would bypass that inline ammeter as I believe they were known fire hazards, and upgrade the cabling to and from the alternator. Go for at least 4awg, and Not those ultra crappy cables sold in AP stores. SAE wire is ~20% thinner than AWG. The AP cables have pressed steel ring terminals. Very resistive, low quality junk.
This place will custom make cables from top quality components, using top quality tools and knowledge, for awesome prices.
http://www.genuinedealz.com/custom-cablesOnce you upgraded the cabling, both + and - to alternator from battery or battery to engine ground(-), and bypass the Ammeter, charing amps into battery should improve.
Once the alternator gives up, then replace it with a higher amp model, and the wiring will be ready to handle it.
Idle speed amperage on Dodges is notoriously bad, and your headlight dimming on Bass notes is likely only noticeable at Idle. This is due not only to the poor idle speed output of the alternator, but the poor wiring leading to the headlamps. It is too long, too thin, with too many connectors, and the result is the lights receive 2.5 volts or less than what the battery is getting from all the resistive voltage drop.
Light output is not linear with voltage. Adding relays triggered by the stock wiring harness to give the headlamps higher voltage makes them significantly brighter, and makes you safer at night.
Often times, a higher rated alternator can produce its higher amperage only at much higher rpm, and at normal RPM's perform poorer than their lower rated counterpart.
Do note lead acid batteries are happiest when they live their life as close to fully charged as possible. It takes about 2 to 4 hours to bring a battery from 80% charged to 100% charged, no matter the charging source. Too many people act like an Alternator is an instant and magical battery recharger, when it is one of the poorest options available to fully recharge a battery. 2 to 4 hours, and that is IF the voltage regulator allows 14.4v to be held for those 2 to 4 hours, which is unlikely.
When your battery dies, consider replacing it with the largest Marine battery which can fit. These are more tolerant of deeper discharges than a thin plate starting battery. But a Marine battery is nowhere near as tolerant of deep cycles as a true deep cycle battery.
12v batteries in the sizes available which fit underhood, even if labelled deep cycle, are built nowhere near as robustly as a 6v golf cart battery.
One can use a deep cycle battery for engine starting, it will just have to be significantly larger to have the same CCA rating as a starting battery.
Many AGM batteries blur this line between starting and deep cycle.
Avoid Optima batteries for deep cycle applications. Odyssey is a much better battery, but when deeply cycled, requires a high amp recharge rate, or it will perform badly.
In Case anybody wants the best of the Best. Lifeline AGM makes the best AGM batteries available. They do not have the super high CCA ratings of Northstar or Odyssey, but they will tolerate and recover from abuse better than either, and still have enough CCA to easily start a 318 at 0f.
I recently got a Lifeline GPL-31XT for a project, and am thoroughly impressed with its performance and build quality.
But at 410$, it better be damn impressive.