The first step in installing a fuel sump is draining the fuel tank. Unless all traces of oxygen are removed from the tank, there may be residual fuel in a vaporized state that could potentially create a nasty explosion when the welder fires up. To prevent this, Buck purges the tank thoroughly with Argon gas. With the prep work out of the way, after centering the sump on the backside of the fuel tank, Buck traced around the sump with a marker, cut out a hole, then TIG-welded the sump in place. It's much easier to check for leaks before the tank is re-installed on the car. Since they won't affect flow in any way, we left the stock sending unit in place, and capped off the hard lines. The factory vent is always retained.