INTERMITTENT IGNITION ISSUE

Get into the service manuals over at MyMopar. Estimate what the alternator is actually off of (late 72? 73?) and read THAT manual and read the part about testing for field current draw on the alternator.

It may be that you have an alternator with a heavy duty field, or partially shorted, that is taking out VR. You may have to look around and find a heavy duty 69/ earlier VR NAPA used to sell one that looks like the Mopar "race" one, and they used to have a heavy duty truck one. It is about square, about the same dimensions "square" as the "long" side of the 69 one is.