[Greg63]

I used the stock grommet and filler neck, and the rubber coupler that attatches to the tank. At the bottom of that assembly I put in an abs plumbing cap (can't recall what size). It is hose clamped onto the rubber coupler.
On the outside I epoxied onto the metal filler neck a gas cap that I made from a horn button from the standard steering wheel from our trucks.

No way you can accidentally fill my cab with fuel.
Greg.