dash lights ? 68 valiant not working

The dash light CIRCUIT is a bit of a trick. It could be anywhere in there, that is "at or in" the cluster, or the rest of the wiring

Power for dash lighting comes "from" the tail fuse, so the tail / park lights have to be working first.

Power goes through the HL switch, through the dimmer control, and BACK to the fuse panel on a tan wire to the INST fuse.

Through that fuse, then out to all dash lighting on orange wiring.

Does ANY of your dash lighting work, heater, radio, shift quadrant?

If not start by checking power at the INST fuse. Parking or head lights must be on, dimmer control twisted to left. Should show power on both ends of that fuse.

From there (orange) feeds up to the cluster. At the cluster, could be the cluster connector, or broken pin -to pc board at the harness pins.

Of course it could ALSO be that "all" of the bulbs or sockets could be bad. Didn't you test it "out of the car?