Someone with more energy can check into it, but many states have a law that specifies the minimum spacing between headlamps, fog lamps, driving lamps, etc.
It is possibly that its also a federal regulation now too.
So having the foglamps in the center, like the 1967 Shelby Mustangs had will be illegal in many states. If you've seen photos of the old Shelby's you may note that some of them had the foglamps out at the sides of the grille. These cars were for states that prohibited the center lamps. I don't remember all the states but I know RI & MD are 2 such states.