[1972gmcsierragrande]

I'm not certain if any of the smog stuff came on 71's. When researching it the gm parts books it show most parts of the system the same for for 1969-70 C models with 396/400, and then 1972 C10-15 w/ 400 and 72 C20-25 Suburban w/400. It never references 71 models so I don't know if those got smog or not. Mine is a 72 GMC 402 half ton which did have it. They took it all off and put plugs in the exhaust manifolds. Here are some pics I found that show a big block smog system still intact.