A-Body tank filler necks

Don't be so fast, the gas caps are different through the years. And also not all dusters and Demos are curves. Only fold down rear seat cars. What I can tell you is that Swinger and scamp will not interchange with duste style because of the contour of the quarter . The end is at a different angle and will not sit flush on the quarter panel. when tightened it could caues the quarter to flex out of shape. Most important is the gas cap though they do not all intercange . the wrong year and it won't tighten or you will not even ge it on. Some have vented caps and some do not . 69 has a small vent tube built into the filler neck up near the gas cap flange I do not see it in this picture. Unless he can give you a specific model and year this was taken from chances are slim it will fit your application propery.