1971 fuel tank vent system....

MOBodyman said
I don't believe there was a canister in '71.

I believe you are right. All cars had the vent control system in 71, just not a carbon can

So..........70's built by and for CA had the evap control system

71 all cars everywhere had the evap controls

72 all cars had the evap control and the carbon can was added to the mix.

Then somewhere 73?4? the vapor can in the trunk was integrated into the tank.