Filler neck interchange/fuel tank vent question

I'm afraid that would siphon. Remember, the original goes clear up front and "ends high." Plus the line going up front had an "anti spill" valve at the end of the tube.

That is the beauty of the original......it acts like a siphon break. The only scenario under which the old ones can siphon is if the tank is extremely full---fuel clear up inside the filler neck........and if the car is parked in such a way.............filler cap on downlill side.........and even then it will only siphon until fuel gets below the level of the tube, and then "breaks."

One thing that might help would be to bring the line up as you say and "let's say" transition the line into a larger vessel......like a large dia. piece of tube strapped to the side of the filler neck........then continue the vent out the top and back down. This would provide some vacuum break and drain back.