Differences between 273 Commando Silenced Air Cleaners?

I've seen 273 Commando Slinced Air Cleaners with a 2" stem protruding out from the side leading to the PCV and some without. What years did it differeniate or is it CA built cars got the side stem for the PCV for emission reasons? My '66 Barra. F/S came with the side stem and is a CA built car.