It's Non vented cap.

If one drove without the cap the fuel would come out the back buy the gallons. (License plate area for those not familiar with a 69 road runner.)

The lines are correct. Yes spectre was known for reversing the lines in the tank but this is both not a scepter tank or reversed inside.

There are no return lines.

If one reversed the the lines the short one would be hooked up to the short one in the tank, fuel would come out for sure then.

What it is, is confusing...?