Got home tonight and checked the voltage. It was about 13.8volts, which I thought was good. As I have been watching it lately on the USB voltage displays, I have seen voltage dipping a few tenths during times if heavy load, such as headlights&engine cooling fan &heater blower use. That has seemed OK. That is, however, how electricity works.
Anyway, I looked around the shop and found that I had an old alternator on the shelf - 95amp? 80amp? Whatever. It's one of the lower capacity ones. So I took the regulator off that and put it in the alternator in the truck. Started the engine - 14.4 volts, no wavering. Let it run a while. Still 14.4volts. Engine cooling fan came on - no voltage droop. Oh, yeah. No idiot light either. I turned on the headlights and my Viair compressor (25-30amps). Still good strong voltage 14.4 - 14.3 volts. I think that indicates my regulator was going bad.
So, here's the plan. I'm going to order a new heavy-duty regulator and install it. Then, the "test regulator" will go back in the smaller alternator. Then, evict the spiders and throw that (the alternator, not the spiders) in the toolbox for trailside repairs. Best of both worlds for very little $$ out of pocket immediately.