2 inch filler neck with screw on cap.
I have a 1970 Buick Wildcat conv. The filler tube is behind the license plate. Even before the motor was modified I would dump gas out from around the gas cap. I tried double gaskets on the cap bending the tabs to make it a tighter seal. Nothing helped. I decided to modify the filler neck and cap with the above product. Now I can pull away from a stop without gas dumping out at all. Prior to the modification I was loosing about a half gallon every time I took off. This was with baffles in the tank to prevent the problem. It's the best fix I found. The easiest fix ever in my mind. Thank you for making such a wonderful product.