Dash problem on 1990 K1500

[Free88]

I just purchased a 1990 Chevy K1500 4x4. The problem is the oil gauge buries itself all the way to the right and the volt gauge goes to the right all the way.
I tested the battery and it was putting 12.7 to 13 volts depending on load. Alternator was putting out 14 volts when I tested it.
The volt gauge also flicks back and forth when you use the signal. Could this be faulty gauges or a bad ground?

Thanks for the help.