Standard Challenger Gas Cap

Are you talking the old style flip top cap? If so there is an adapter that a member is selling. See link below.

http://www.forabodiesonly.com/mopar/showthread.php?t=53282&highlight=flip+top+cap

No I was looking for the standard gas cap, it is similar to the dart but is dished. Maybe I look at a billet gas caps. I want it to be flush with the body panel.