I am ready to install the gas tank sending unit. It is a Classic Gauges product and after reading the directions I am confused. It tells me to cut a 1 5/8 Hole in the tank and then insert the unit into the tank and then attach it using the 5 screws provided into the "pre-drilled holes". What pre-drilled holes? The directions to this point does not mention drilling holes. Besides it looks like the screws need a threaded hole. Anyone know how this all works?

http://good-times.webshots.com/photo...99708909ITmsUH

As you can see the tank came with two outlets, one inlet, and a vent.