Basic facts...The Pertronix III is a multi-spark ignition. That makes the hot wire between the module and the coil part of a resonant system and voltages you measure across the coil are meaningless.

The MSD6 is a capacitive discharge system and the capacitor hits the coil with tiny bursts of high voltage, somewhere around 450 volts, one hit for every spark. When you put a voltmeter on that it measures the "sorta" average voltage. Again, meaningless.

I have run the 732 "Race only" voltage regulator on the street since 1984. It's the same internally as the 731. There is nothing inherently wrong with either regulator. My charging voltage measured across the battery terminals is roughly 14.3 to 14.5 volts, just what a modern maintenance-free battery likes to see. Some have suggested it's race only because it does not bias charging voltage to the temperature. Could be, but it is meaningless as well because it just flat works. My batteries last, on the average, 7.5 years. One thing this regulator did is keep enough charging at idle that my headlights do not act as a visual tachometer any more.

Grounds are very important and need to be policed every once in a while. Also, the suggestion to ground directly to the alternator case or the battery negative post is right on.

Finally; when someone shows up with a "problem" the first thing to do is analyze if it really is a problem. Everyone jumping on their horses and riding off in all different directions does nobody any good. The stock answer to buy a new one doesn't help either, not until the real problem is identified. In some cases the best suggestion would be to get different friends, if the friends are terminally ignorant. (Especially Chevy Know-it-alls.)

Warmest Regards,
R.