I'm in the process of mounting a Cat fuel filter setup on the frame rite in front of the fuel tank, can any of you who have done this tell me which line is the one I need to cut to connect my fuel hose to, because when I'm underneath and I'm looking at the inside of the frame, there are 2 metal lines running from the tank to the front of the truck, the only difference is one line is big (About 1/2) and the the other is smaller.

The larger one is the supply and the smaller one is the return to the tank.