No, the grilles are not directly interchangeable, but yes, you can use the later grillr in an early 1200. The difference seems to be in the little lugs that the grille attaches to along the top of the RSP. The coupe & later utes use a longer mounting lug to reach forward to meet the grille, but what's the problem with geting a real grille.

The original 1200 ute grille was a cheaper version of the car one & these car grilles look very good, unless you leave off the central badge, then they look ummmm, .... incomplete.