Tank filler and vent

[vince1]

The Jeep tank I have supported between the frame rails has a 1" fill nipple and a 3/4" vent nipple. The vent nipple currently has a rubber plug on it. Seems awfully small for the fill but that's what it came with. Am I correct in assuming that the two get connected in the fill pipe? My plan is to cruise the junk yard looking for something suitable for either up through the box into a rear corner or out the side. Advice and suggestions greatly appreciated. Thanks.