No dash lights

Any chance all the bulbs are burned out? Does the dial lamp in the radio work? What about the heater controls?

The wiring diagram is hard to follow because they do not actually show the head light switch or what goes on inside it, but we should be able to figure this out. This partial diagram I posted shows the layout of the fuse box which will make a good starting point. My nifty blue arrow is pointing to the signal flasher. Use that to verify the orientation of the fuse box. The red and green arrows are pointing to the two ends of the fuse in this circuit. Measure the voltage on both of those points, first with the head light switch off, then with it in the tail lamp/running lamp position, and tell me what you find.

Also, check if the tail lights are working properly.

Next, there needs to be 12 volts on the gray wire in the head light switch connector at some point. Back-probe that wire and tell me what you find.

I am going to try to find a different diagram when I get home later. That might be just different enough to shed more light on which place to go next.

Did you measure the voltages on the two sides of that fuse?

Check for power at the rear of the cluster that goes on when the lights turn on. Sorry no wiring diagrams for this truck. :( If you find the wire that gets power it must be a ground issue. Here is a guide to help you with the testing:

https://www.2carpros.com/articles/how-to-check-wiring

Please let us know what you find. We are interested to see what it is.

Cheers, Ken

Dandy. Next, check for 12 volts on the gray wire at the head light switch. Tell me if you have that all the time or only when the switch is pulled to the "tail light" position.