[jocko]

When I lived in CA, C10s required commercial tags if the bed was open. If bed had a cap or tonneau, it was not required. It drove me absolutely nuts that had I had to go weigh and register my 66 C10 swb as a commercial vehicle. Maybe things have changed and CA has seen the light.

Regardless, 2 of the 4 72 402 suffix codes indicate that there was indeed an AIR-equipped 402 built for C10s and C20s (trucks) in 72. And the other 2 suffix codes indicate that a C20 or C30 could have a 402 without AIR. Maybe the smog 402s in C20s were just uncommon, or driven by an individual state requirement.

I'm still not quite clear on what drove whether or not AIR was required on a C20, truck or burb.