[OrrieG]

Stock tank or aftermarket. There is a standard pattern for fuel sending units. If you bought an aftermarket tank it should have came with a standard fitting for the sender. Sounds like you have something that was made without the sending unit plate. The fitting is about 1/8" thick so it will not deflect and will seal tight. The sending unit is attached with 5 machine screws and a gasket. . Don't use sheetmetal screws on the thinner guage tank, you will have a hard time with the metal oil canning and leaking and the screws possibly backing out.