I believe it was somewhere around 1968 that the auto manufacturers changed the headlight/parking light set up so the parking lights would stay on when you turned on your headlights. That way, if you had a headlight burn out, there would still be a light glowing on that side of the car and other drivers wouldn't think they were approaching a motorcycle. In putting my '66 Special together, I discovered that the headlight switch had an extra lug that was powered in both "On" positions of the headlight switch. By carefully removing the parking light wire from the headlight switch plug and moving it over to the slot in the plug corresponding to the position of the unused, powered lug, the parking lights come on when the switch is pulled out to the first detent, and they stay on when the switch is pulled out to the second detent to turn on the headlights. I've been running the car this way for two years now with no ill effects on the switch or overloading of the lighting circuits. This simple change adds a measure of safety to operating your pre-1968 Buick after dusk.