Look a little closer, and the wires are probably labeled, Tail, Park, and Headlamp. The tail lights come on in both Park and Headlight positions, while the park lamps usually don't burn with the headlights on. That's the way things were done in 57, now a lot of vehicles run park lights anytime the engine is running, and/or they keep the headlights on at a reduced level during daytime running.
Jerry
