Fuel tank lines

I'm having my tank redone.  I looked in the service manual and cannot find an answer to this question.   My tank has three inlets.
1.   Big inlet where the gas pumps in from the gas pump ( where are you pumping gas in when getting gas at the gas station )
2.  One small Inlet right next to the sending unit. This is the hard line that goes up to the fuel pump  

3.  Lastly there is a third line a stem on the drivers side of the tank.  A rubber hose hooks on the stem and I'm not sure where that rubber hose goes. I was thinking that was the return line either from the carburetor or the fuel pump but since I was told we need a vented fuel cap I'm assuming that this van does not have a return line. Can anybody tell me what that third stem is for?


Thanks

The filler tube might have a smaller fitting on it so that as the gas goes down into the tank, it has to push air out back through another hose near the gas cap......

,,,this is how Chevy does it,,,,

Oh. I see. Thanks. Kind of new to these vans and not sure what the extra line was for. I need to follow it to its end point this weekend. Thanks!