I can really only get appearance mods right now, because my parents don't want any warranties voided. Here is what I'm thinking of getting at some point(going for a blackout theme) for my Red candy GT:
Black Ford Racing rims
Ford Racing GT500 exhaust, or Ford Racing sport exhaust
MMD Window louvers( not sure of getting either body color, or black)
A black 5.0 or GT gas cap
RTR or Shelby black stripes
and an RTR rear spoiler.
2013 GT Premium, Red Candy Metallic, Recaro seats, Electronic package, Strut tower brace, Sway bars, SHR flush mounted window louvers, RTR street-spec axleback exhaust, Ford Racing Boss 302 Side Exhaust, RTR wheels, 50/35% Window tint, Steeda black shorty antenna, and Ford OE Matte Hood Vents.