Ok, I checked the battery gauge wires today, and when I started the truck it works! Apparently it was working last night, but I did not see the needle move in the dark (gauge lights were not working).
Here is the battery gauge with the engine started cold.
Here is the oil pressure gauge started cold.
Here is the temperature gauge. Had to wait until the engine warmed up for this picture.
Now all the gauges work except the speedometer.
The speedometer has NEVER worked. I noticed that the mileage on the truck title was exactly the same from 20 years ago as it was when I bought it. So today I got under the truck, disconnected the speedo cable, and spun it with my fingers while my son held the other disconnected end. The cable spun freely. So this means that my speedometer drive gear is going to be checked next. It must be damaged or something.
Years ago a forum member taught me how to repin the idiot light plug to work with gauges. I sure am glad that he did, and I always use the charts on here to assist with it.