For replacement parts I'd recommend Newtakeoff.com. I don't think they have V6 body parts but if you wanted to upgrade to the GT look you could do so cheaply through them.
I'm not sure where to go for body kits and I think most people would advise against this. If you do want to get a body kit though make sure its not made of fiber glass. They are much cheaper but usually don't last long.
2005 Ford mustang V6.
18 years old. 0 accidents. 1 ticket.
The ticket was for going 27 MPH in a 25 can you believe that garbage!
I stuck it to the Man and the Man stuck it right back to me.