OK I've tried to explain this to you. This is the last time
1...Go to MyMopar and download a 69, a 72, and the 73 service manuals and look at that section on the evap emissions and you will see the changes over the years
2...ALL TANKS need a vent
3...Up through 70-71 when tanks were vented BY the vent tube in the filler, the vent connected UP HIGH in the filler tube and THAT CONNECTION formed a "vacuum break" so the thing did not siphon. The only time that vent would overflow is if the tank was somehow extremely full and parked on a "sidehill" with the filler side down, and ONLY THEN it would spill fuel at the vent until the level dropped below the vent connection, and stop
4....None of the caps are truly vented. Up through the evap cars, the cap was SEALED. Caps after that are pressure/ vacuum "relief" and they are NOT considered vented. RELIEF
5...With the evap tanks there MUST be a way to prevent siphon. Some models had the tank in the trunk "vapor separator" and this allowed some fuel to come up into that tube and then drain back to the tank. THE LINE GOING to the front comes "up high" in the engine bay
6...The later cars/ tanks had a vapor separator IN the tank, and only ONE vent line leaving the tank. With those model cars it is more important than ever to keep the line to the front UP HIGH to prevent siphon.
That is all I have to say. You do not seem to want to believe anybody. So do whatever you want. I do not care