...refers to the more rounded rear wheel wells/fenders. I have noticed that Contemporaries, FFRS and one other marque have a wide flare, but the actual wheel-well/fender are quite narrow. This shows up especially well in front quarter shots from slightly above (a tall photographer, maybe..
I have noticed that the Arntzes and Butlers have "tweaked" rear wh/wells. You can put 18" in wide wheels in there-----if you could find 'em!
So-o-o- did SHelby only make a few of these? I assume the reason he did was for wider wheels/tires.