Ok, so you can change the front out; can you add the mesh like grille in the rear of the coupe like the vintage, or custom some piece of mesh?
OK, I think you're really asking two questions here.
1) the vintage pack cars use chrome mesh grille inserts and yes if you buy them, at least the front one is pretty easy to change.
2) the 2005 and later cars have larger front and rear grilles (like the GS) and you've probably seen a vintage 2005 or later - they are certainly distinctive!
To swap the front and rear bumpers out for the 05 and later style is pretty expensive, there have been a few threads on this.
2004 non vintage, front
2004 non vintage, rear
2004 vintage, front
2004 vintage, rear