Gauge Rebuild

So for this winters project I need to rebuild/repair my gauges.

Fuel fill seems to work, temp is out (could be sensor), gen and sorry I dont recall idiot light have never been on, speedo bounces +/= 15 mph.

So tell me the good, bad, easy, hard!

The gauges are usually fine.  Check out the senders and wiring first.  Basic troubleshooting.  The gauges and oil light are activated by voltage to ground.  Start at the sender.  Ground the wire there and see what happens to the gauge or oil light.  If none of them work, check the other side of the gauge or bulb for 5 volts with the ignition switch on.  There's a small regulator box on the back of the panel that cuts the 12 volt battery power down to a cycling on/off that approximates 5 volts.  If there's no power out to the gauges but the oil light is getting positive power check power into and out of the regulator  If nothing's going into the box check your feed through the fuse block (on the headlight switch) and ignition switch.  

The fuel sender is a variable resister mounted into the top of the tank. It varies voltage to ground based on a float in the tank.

The generator light's wiring is a bit more complex but usually your only problem there is a bad light bulb or disconnected wires.

I'm not telling you much, as your question's pretty general, but maybe that will offer some order for testing.  Usually these trucks are a mess by now so expect to find multiple little problems that have to be sorted out. Fifty years of things breaking with no repairs winds up with nothing working.  Give it a few hours and you should have them all fine.

I found nothing odd or difficult about these trucks' gauge circuits except that the shop manual schematics aren't always 100% accurate.

And the speedometer can be fixed by lubricating the cable. Disconnect at one end and slide out the center wire. Clean and lubricate and slide it back in.