Technical 1967 Buick Wildcat gas tank

The fuel sending unit has the fuel pick up tube & return lines, but the tank also has two more tubes at the top front corner of the tank. Can they be used as pick up & return points for fuel? They were unhooked and open when I dropped the tank.

 

Both of those tubes are for the vent system, which on that car is rather complicated.

 

So are they suppose to be hooked up to anything? I can feel one tube that runs across the inside top of the tank. It disappears behind a baffle inside the tank.