Exact voltages are important when troubleshooting. "About" does not tell us a whole lot. A battery is considered functionally charged at 12.5Volts. With the engine running you should see more than 13 volts across the battery + to -.
Now, in your OP you said the alt light goes off at high rpm. Take a voltage measurment at this high rpm point when the light is off. Have you ohmed out your fuseable link?

 

I took apart each connection between the regulator, alternator, and solenoid and tested them for continuity. They all seemed good including the fusible link. Made sure the connections were clean and tightened up good. When I was done,the ALT light went out after I started the truck!.
I don't know where the problem was, exactly, but it seems good now. One more problem down!

thanks fellas, I do appreciate the help.
-Steve

 

sometimes a good cleaning, or just a tear down, can make a difference on 30 yr old electrics!