It sounds like you have made a choice, you also now know the big trouble spots, bulkhead and ammeter studs that get loose, many ways to fix those issues. The voltmeter just told you more than the ammeter...15 volts is too high. At normal engine temperature it should be 14.25. Stock mopar 100 amp alternator voltage regulators, are not the same as the 65 amp and lower regulators, charge at around 14.75 cold, 14.25 at 70- 80 degree ambient temp and 13.8 or less on a 100 degree day. Some aftermarket regulators run over 15 volts, some do not temperature compensate, harder on the battery, and the wiring. The voltmeter will also tell you when the alternator or regulator fails by showing 16 volts or more, and shows failure by showing low voltage. An adjustable voltage regulator is available, but the one I used did not temperature compensate, just allowed you to set the voltage. Some of the post in various links are pretty funny as they say the factory went to voltmeters because it was cheaper, I doubt that. Modern charging systems measure the temperature of the battery, and outside temp, maybe even other things, and control it with a computer with the battery hooked directly to the alternator stud. I guarantee you was not cheaper to do that, just way smarter.