jimrr - i own a 1972 Series 3 NA spec. It was bought new in 1972 in Manchester NH. I bought it from the original owner 20 years ago, it was still all original. It has the emission control set up as described in the diagram i posted and it is still in working condition. About 6 years ago i replaced the hose that runs from the fuel tank to the overflow tank and the hose from the overflow tank to the charcoal canister. I also took the charcoal canister apart and cleaned it and put in fresh charcoal. I have replaced the original Lucas distributor which was also different because of the emission control set up. It also had an anti-diesel solenoid attached to the zenith carb which i also replaced (the carb that is) the solenoid is no longer part of the set up although I still have it somewhere.
Mike