@joules posted:It appears you have an extra bung someone has welded on top of the tank?
"Added"? That is the exact location of my original fuel "pick up". I will admit that it looks a little different then mine but I wouldn't rule out the original being replaced with a '72 used tank and that tank having a repair to it on the flange.
Take the plug out. If it has a tube in the tank going to near the bottom, then likely it is an original "early" tank. In any case it would make an excellent location to the return connection.