Right, those weren't factory equipment til '72. I'm saying there's a better result by keeping the tank with the vent fitting and adding the charcoal can, rather than changing the tank.
cap that has been on the car for decades looks like to me is vented. it has a little hold inside of a plastic piece on the underside of the cap.
That's a pressure-vacuum cap as described at the linked article. Factory equipment on '70+ California and '71+ 50-state/Canada cars.
car was running fine and I drop to a gas station and waited for my wife with the car idling. it was fine, then about 10 min later it started to act like it was going to die and it was down on power.
