Just a thought, is it possible that Ford left the 03 Cobra grill-less to aid cooling? Seems to me like it is very hot under the hood. It also falls in line with why they got rid of the honeycomb grills as those cars ran a little hot.
I think the billet grilles look fuggen awesome on the 94-98 stangs... especially with a pony or a horse still in it. However, I think that they dont look quite as nice on the 99-03's because of the larger grille opening. I wouldn't buy one for mine unless I had a 94-98