These aluminum fuel tanks are designed to fit between the frame rail and rearward of the axle on 1955-59 Chevy, GMC trucks. By moving the tank out of the cab, you gain much needed room to allow for further customization, increases fuel capacity and safety! Made of heavy gauge aluminum, these tanks offer a light weight design.Vent bung size is 1/4″ NPT. Fuel feed bung size is 3/8″ NPT.