The corrosion might not be the center contact for the bulb. All the dash lights are connected together with a blue and red wire, that goes back through a connector, to a fuse and then to the light switch. So, unless there is something wrong with the wire, the power to all the dash light should be the same. However, the return is made through the metal of the dash itself. Where the bulb snaps into the dash must be clean and the connection from the outside of the bulb base must make a good contact to the metal of the socket. The dashboard metal easily corrodes especially where connection to the bulb socket is made. Hit the area around the hole with some sandpaper to insure good ground contact.
One other test is to put a clip lead on the socket springs and touch a good ground or plug the socket into a different hole.

 

So here is another weird thing, the gauges don't really work. The gas gauge only reads half a tank and the rest of them don't work at all really. So, I replaced he voltage regulator...nothin, still doesn't work. Thoughts? Could these two things be related?