If that is your actual schematic of the wiring you have more than one issue. Looks like the only ground path is through the door switch. So the door has to be OPEN plus the switch turned ON before you will get a map light. I have a 73 chassis manual in the truck and will take a look. But I would wire both the glove box light and the map light to an always "on" hot lead on one side, then pick up ground through their respective switches. Ground the LEFT side of your switch in the drawing above. And hook the door switch to the RIGHT side of the map light switch. The headlight switch should not even be in the circuit whatsoever.