if memory serves me, what's under the headlights are running or "parking" lights and not turn signals. you can adapt them to turn signals by rewiring them, and adding the needed pigtail with 2 contacts. federal law regarding turn signals wasn't mandated until i think the early to mid 50's. i have seen guys (like me) mount foglights behind the grill where they couldn't be normally seen, but are extremely bright when used as turn signals.
