As I recall from Thomas Mutch (Driver & Facility manager), the taillights, the rear bumper, and a support brace in the doors....& the chassis.
Actually the tail lights are just lexan covers with decals on them , the rear bumper is a carbon piece from Matech and my doors do not have any support brace .
The chassis , floors , rear frame extensions to the bumper and front bumper frame are from a production GT .
The rocker sills and rockers panels are stock GT and the side marker lights are from the street car ( which is a Land Rover part )
I think some of the early cars had stock GT taillights but perhaps the pricing from Ford was the reasoning for the switch , I am putting Ford taillights in mine