Let me try to help clear some of the confusion here. Alternators are controlled by voltage regulators. These are not current regulators. They sense voltage. An alternators output will continue to rise to load until the specified voltage is achieved. As more load is applied, the more voltage drop you will have, hence, the voltage regulator will apply more voltage signal to the commutator, until such point it reaches it's maximum output. When an alternator reaches it's intended set point for voltage, it decreases voltage to the commutator, thus decreasing output. If you have overvoltage issues, then you have either lost voltage sense, or the regulator has failed.So how does an alternator know when to produce more (or less) current?
One point of suggestion to all who read this, the body of the vehicle itself, provides the lowest resistance for all grounding. Run your very large gauge cable, as short as it is possible from the negative post to the body itself, and at your amps ground with shortest large gauge cable directly to the body. Also, do the same from a place on the block to the body. Positive feeds must home-run to its intended feed. Just a word to the wise.