Apart from the work you already mentioned, for a "more correct" GTCS, the grill will need to be corrected, the side scoop inserts are missing, and maybe the foglights may need changing. I thought there might've been an issue with one of the twist lock hood pins also.
The paint, though it looks nice in pictures, from what I remember, needs a little help, maybe repaint (unless the current owner did some work here).
Just take a close look at everything, note the things you don't like or needs correction, and see if you're okay with your list, and decide if it's worth it. Also, let the seller know and maybe he'll lower the price for you.
Also, check with the Marti Report people on this car's authenticity if you're serious about buying it.
Good Luck