breather for open tank vent
i know your post is old but i just had my tank out of my 69 and found a 'purolator' breather that fit right in the open vent line and it tucked right up against the trunk pan. ther is a little filter, and the opening is sideways, so i spun it around so the open side was against the trunk pan. should still vent but wont slosh fuel out. it was real messy under there.