The original alternators' max capacity ranged from 30 to 45 amps, which isn't a lot by modern standards but is plenty for stock or reasonably-close-to-stock cars. The output at idle isn't as high as in newer alternator designs (or newer versions of the Chrysler alternator), but the problem of almost no output at idle is often greaty aggravated by the installation of a "remanufactured" alternator from the parts store. These contain mismatched components from multiple different original alternators, which are physically interchangeable but don't work properly together. Or, they have been "upgraded" with cheap "high amp" kits which permit the alternator to put out more than original current, but at the cost of much poorer low-RPM output.
And then there is the question of whether your alternator is healthy. There are many problems that can affect any alternator and reduce its output. An open or shorted diode, or another fault in one of the alternator's winding phases, can cause the alternator to carry on working, but with reduced efficiency and output. Often, such alternators will pass the so-called "tests" you can get done at the parts store.
There is no such thing as a "constant output" voltage regulator. The term was made up by whoever was writing fiction for the Mopar Performance catalogue a bunch of years ago. This fictional special voltage regulator was in good company; there were also the "high compression 9:1" slant-6 pistons that were in fact ordinary production items and a bunch of other pretend-performance parts. Furthermore, the quality of the electronic boxes Mopar sells (voltage regulators, ignition boxes) is inconsistent and generally poor these days.
Fortunately, there are many good options for voltage regulators.
Other threads worth reading here and here.