Overcharging - alternator suggestions?

I don't follow powermaster. How is this supposed to be wired? Is it alleged to have a built in/ built on regulator? It appears one brush is grounded?? like the pre 70 systems? If the VR is external and that is so, you must use the older VR. Part of the problem is that many of those older VR will not handle the field current on a modern "upgraded" high output alternator.

In other words you need to find out what you have there

It appears maybe you an convert it to isolated brushes (incorrectly known as "dual field) which means one more wire will allow you to use the much better 70/ later VR

On that note, you need to find a quality one or NOS. ANY external regulator MUST be grounded. Use star lock washers and or a dedicated pigtail