Oh my gosh....I just found and posted those links a few days ago and now they appear "gone".
What it is, is a tube that connects the front and back fuel bowl vents. The extension tube has a number of vent holes along the top. The idea is that if fuel is sloshing out the vent tubes,, it merely travels to the opposite float bowl. The hoels are needed to maintain fuel bowl venting.
Sorry about the confusion.
EDIT: I think the cut-and-paste messed up. Here, try again:
http://www.holley.com/data/Products/...99R10268-4.pdf
http://classicbroncos.com/tech/offro...4-barrel-carbs