I saw something related months ago and cannot find it again with search, so here goes.

When i turn my key to "ON" the tach jumps to 500. When I start the truck, the tach says right around 2500, but i know for sure that it is not that high. I think that it is idled right. or dang close. While driving, I think the tach may go up to around 3000. My oil "gauge" is flaky too, even more flaky than factory. Sometimes going down the road, it will say no oil pressure; then sometimes it will start working all the time. I also expect that the temp "gauge" does this as well. Periodically, while stopped, or driving real slow, I see the voltage gauge drop about halfway for just a split second.
I just recently noticed my "Cruise Control" light does not come on. Since noticing that, I haven't had a chance to check other lights.

Could this be a fuse? I seem to vaguely remember seeing something about replacing a resistor or something in the instrument cluster. Does this seem like a problem caused by such an issue?

Also my radio has been getting staticy sometimes lately. It almost sounds as if the speaker wires are shorting out briefly. After a very staticy drive, I began beating on different parts. I discoverd that if i beat on the door panel, the radio seems to fix itself. Seemingly confirming my prognosis. Could this issue also cause my dash issues?

 

Sounds like you are losing negative (ground) to the gauge cluster. The dashboard negative is up behind the parking brake pedal.

The tach jumping around sounds more like a short in the harness though.