I sold an NOS "70" Duster fender years ago and it had the depressed indent for the antenna mount.Many years ago at the Mopar Nationals I saw an NOS Duster fender in factory gray primer w/correct part # and it had the the normal body curve for the antenna.The one I sold was also red oxide like the one on the ebay auction.

1970 Dodge Charger R/T S.E. 1969 Dodge Dart GTS 440 M-Code 1970 Dodge Charger 500 383/4-speed w/A.C.