Today the symptoms have all but disappeared. There still is a little dragging when starting the truck, but not as bad. Today I ran the truck with the lights on, radio on, and fan on high, but no fluctuation of the gauges. The altimeter did seem to be little further to the left of center than usual. Thank you for any ideas .
Electrical problems are very difficult to find.
On your truck, we would check all the ground wires. From what you describe, somewhere there may be a loose or bad connection. The turn signals and power windows suddenly quit at the same time on my 1988 Subaru. I checked the fuses and they seem to be fine. Check fuseable link in the engine compartment.