The tail and front lights ground through the light housing. The two wires on the front lights are park and turn and the two wires on the rear lights are for brake and tail. You must have the housings grounded good for them to work. You may need an extra ground strap from the bed to frame because of 50+ years of corrosion in the original mount bolts.
Both headlights should burn in both positions. You could have a burned out low beam on one side.
The red indicator is for high beams.
