[PbFut]

A 1972 c20 has a commercial classification, so no calif smog equipment is/was required. C10 required smog as it was not classified commercial. It is why a c20 is more expensive to register in California because of commercial class. The c20 has commercial plate allowing you to park in yellow curb commercial zones. Useful in urban areas of LA, SF and SD. The Chevy Suburban, even the c20 Suburban was classified as a passenger vehicle so smog was required. You can get a C20 registered as passenger if you have a permanent camper on it to save a few bucks but a sharp eyed smog tech could have caused problems. Not a issue now. We are past inspection dates. If you need info on BB smog parts, I would look to the C3 Corvette owners. They likely have the info given there were a lot of BB Corvettes from that time. They were putting pumps on 250 sixers as far back as 1967 in calif. The air injector port was actually in the head, not the manifold. I owned every car/truckmentioned in this post except the suburban at one time or another.