Oh, foot, I completely missed the 2013 part, and it looks like jsimmons did as well.
Looking at photos of the various 2013 models, my guess -- and it's only a guess -- is that the bumper cover and lower fascia is the same for all cars, and there are block-offs in the openings where the GT/CS and V6 Pony Package fogs go. So all you should have to do, again apart from whatever you do for the upper grill, is buy the non-blocked inserts and the fog lights themselves.
Did you order your car, or are you buying it off a dealer lot? There have been some sightings of base, non-CS GTs that have the CS/PP fogs installed at the factory, with the V6 upper grill that has no fog light openings. From what I've read, all Canadian GTs will be built this way (something to do with their daytime running light laws) but I've seen at least two reports of US cars built the same way. Whether this was a mistake at the factory or something new for the base GTs is unknown. Point being, if your car is on order and you've not actually seen it, it's possible you won't have to do anything at all.
2012 GT Premium Coupe | Performance White | 401A Charcoal+Grabber Blue | Comfort Pkg | MT82 | Boss 302 Shift Knob | 18" Pony Pkg Wheels w/Brembo Pkg Center Caps | Boss/CS Front Valance | Scott Drake 5.0/Tri-bar Fender Emblems | FRPP Strut Tower Brace | Redline Hood Struts | GT500 Rear Splash Guards | Rear Spoiler Delete | Sound Tube Delete