Tanks, Inc Venting

I have a 70 dart with a non vented gas cap, however my fuel filler neck is vented.

I bought a tanks, inc tank with their sending unit and a walboro pump. the sending unit has a nipple for venting and so does the tank. They supplied a "T" to hook these together but the rest of the directions are kinda vague.

Where do I hook the final vent line to? The filler neck, I believe just vents into the atmosphere, below the trunk floor.

Thanks!
I'm running a tanks Inc in a 68 barracuda. I tied the 2 tank vent lines together and am just running the filler vent.