OK, so you have a '71 and a '73. Since your picture shows an external regulator, I'm guessing that came off the '73. As sfdon wrote, "Change your regulator asap". Is your electronic tachometer still working? A bad regulator fried my tach several years ago. The Pertronix ignition too, which was a bigger problem since I was several hundred miles from home. Those regulators are readily available, since they were also used on Mercedes, Volvos and Alfas of that era.
Was it that corroded when you installed it two years ago? Man, that looks nasty!