[sloGMC]

I'm not sure where this thread is going, but if anyone has questions regarding what emissions equipment were installed for various models years the service manuals should have a small section dedicated to it. For '71, PCV and C.C.S. were the only "installed" emissions equipment for 20 and 30 series trucks. Evaporative Control System (the tank and fuel bowl vent tubes to charcoal canister) are only for series 10.