Another issue I need to figure out with my 77 is the headlights haven't worked since I bought it. I don't drive it too often, so it hasn't been an issue, but I need to get this fixed.

Is there a wiring diagram for this model truck? If not, what's the next best option to get this figured out?

 

I don't know much about the 77, but my 83 has two green plastic connectors at the battery. Pull them apart, clean them up, and reconnect, see if that works before you go deeper. Worked for me one night in a jam, they had gotton dirty.

Fishhook