I'm right there with you. My late 260 race car has a blank cover plate in the sending unit hole and I can't find a replacement. I compared the '74.5 to a '75 and they are different. The arm lengths are not the same, so the readings will likely be off. The '70 - '74 tanks are different. I believe you will have to limit your search to a proper used '74.5 sending unit as they are NLA new.