Gas cap question/pic

Take a look at this gas cap, this is not my car but a picture I found on-line, I have the same problem as the cap does not fit correctly in my opinion, shouldn't the face of the cap be flush with the body panel and not stick out. I ordered a stant 10800 cap which is supposed to fit but it doesn't, any help on this matter will be greatly appreciated, thanks, Ed (76 duster)

Does anybody know where to get the correct gas cap?