Here is a pic of the wheels in question, not sure if they are knock offs or what, but look a little different than yours Jim. I dont know a whole lot about the cobras. I have fit the 275/60 under my other coupe with heavily rolled lips (like this one) and it only rubbed on pretty hard bumps.
WTT 4 lug 17" Cobra Rs for 4 lug Draglites - Corral.net : Ford Mustang Forums