I have no wiring diagrams for your model year. The instrument cluster lamps may be wired off headlamp switch. There may be a fuse for instrument lamps, check the fuse and check for voltage at the fuse.

As far as the fuel gage, That voltage should come from ignition switch, key on. You may have to get at the gage itself and check for voltage. You can also check the wiring at the gas tank. If two wires use digital multimeter between those two wires key on, do you get a reading?