I'm also curious if your car originally had some kind of venting. I'm only familiar with my 1967 Barracuda with the vent attached to filler tube and then vented below the trunk. It sounds like you want to do something like that.
My filler tube looked good from the trunk, but when I pulled it, it was badly rusted where the tube was submerged in the tank, and I just replaced it. Cost was about $70 from 521 Restorations. Consider you how much your time is worth. BTW, the new tubes are temporarily not available from 521.
