Did the 1976 duster come stock with interior lights

Of course they did LOL. These might be "A bodies" but they aren't "Ford model A" and they weren't built in the 1920's

There are several things, as that circuit is a bit of a trick

The headlight switch receives power from TWO sources---one only runs the headlights, and the other one supplies the tail and park lights----and the instrument lamps So, to start with, the park/ tail lamps MUST work

That power goes through the instrument dimmer control in the headlamp switch SO YOU MUST have the light switch knob turned to the left to brighten the dash lamps. Twist and wiggle the switch because they get dirty

That power then comes out of the instrument dimmer, goes TO the fuse panel to the INSTRUMENT fuse which is usually on one end of the fuse box. That fuse must be good. All dimmer controlled instrument power then feeds out to the various lamps in the instrument panel.