anyone use powermaster alternator?

As others have said, there are MANY causes

1 If you have the later model squareback alternator, it in itself is not that bad, an improvement over the earlier roundback series

2 Poor headlight sockets, poor grounds at the headlights, and drop in the entire headlight harness, from the switch, through the dimmer, and the drop in the bulkhead connector. The answer is RELAYS. But do NOT ignore grounding, either.

3 Make sure the charging system is actually up to snuff, that is, that the alternator is putting out what it should, and the regulator is actually at the voltage it should be.

4 SERIOUSLY consider bypassing the ammeter. Read the MAD article for the hows and whys of what bulkhead connector drop causes

http://www.madelectrical.com/electricaltech/amp-gauges.shtml

Some of us, depending on what dash you have, have converted the ammeter to a voltmeter. On my 67 was an easy project:

http://www.forabodiesonly.com/mopar/showthread.php?t=119480&highlight=ammeter+conversion

5 On my own car, which no longer has factory wiring, I used a junk Voyager relay box like the one below. You can also get similar boxes from Bussmann which can be configured in many ways. My box has relays for ignition/ charging, pump, headlights, and anti-theft, and fuses. It's all powered right off the starter relay stud, mounted on the left fender apron