The tank is vented through the cap. I didn't understood the sending unit description on the vendors website. The sending unit that my tank has has the flange with a bolt for the wire conection and a 90º elbow that is connected to an "L" shaped tubing that goes in the tank, where the reostat is attached in the middle. The guy had the fuel line that goes to the pump, attached to this elbow. What I noticed is that the sending units of the websites some have this elbow and others don't. Which would be the one to choose? The tank, as I told, has a plug in the lower part (I guess is for draining, rather than for the fuel, but dont' know). GMONIZ, this is the 50's-56 salad truck. I don't know if the tank is 54 or later, since I don't know the difference between this and the earlier type. I'll try to take a picture tomorrow, to post.
Thanks