So, I found this trailer for GTHD posted by IGN. The first car shown is… a Nismo R33 R-Tune? It hasn't appeared in any GT game yet. It may have had the same fate as the Premium Impreza rally car (which is still unknown)
I think those are all real physical cars instead of 3D models. They might have had access to them for photoshoots and used that in the trailer, but those close up shots are way too detailed to be any game models from <2007