[Double Venom]

We/I used Fords "Roll Over" valves for their F150 Vans. I think we cut a true 3/4" hole in the top of the tank. The Ford valve came with it own sealing rubber grommet. Simply install the grommet, then the valve in the grommet and a line to the valve. Cheap and really worked well -- how ever you would have to be careful how you ran the line as you "could" end up with fumes in the car.