That may or may not be correct IT IS SO FUZZY I cannot read it. Go to MyMopar.com. Download the FREE 73 service manual, WHICH GOT THERE because of GUYS RIGHT HERE
The service manuals over the years have sections on fuel, the tank, and emissions which lay out how these were put together and how they worked.
THE 1/4" line coming up from IS THE VENT. There IS NO VENTED cap, that is, not operationally. The cap has pressure/ vacuum pressure relief valves, they are NOT vents. Be careful of caps. They changed nearly every year after the evap stuff got rolling