The older cars (before charcoal canisters) vented to the top of the filler neck. There was a hard tube from the tank parallel to the filler neck, with a short rubber hose at the top connecting to a nipple on the filler tube just below the cap. This is meant to work with a vented gas cap (I assume your car would have a non-venting cap for emissions reasons). I suppose you could run a similar tube anywhere so long as it exited outside the car (don't want to fill the trunk with gas fumes). Or switch to a vented gas cap. But don't run without any venting -- it could collapse your gas tank under certain circumstances -- I have had it happen with a clogged vent pipe.
