Smoke from breathers.

As mentioned, the factory setup was a hose from the oil cap/breather to the air cleaner. I think the purpose is to flow either way - suck clean air from after the air filter to the crankcase (by PCV sucking) or to vent blow-by that overwhelms the PCV under hard throttle into the carb. My 69 Dart had that setup (federal) and I think CA cars much earlier (recall my 65 Dart was). After-market chrome air cleaners usually have a knockout hole in the bottom to connect a hose to the bottom.