My thought was the opposite. If you were trying to return the car to factory-original, re-installing the original grille would be worthwhile. But since the important numbers-matching stuff is all gone and the grille doesn't have a number on it anyway, there's no more importance attached to one grille versus another.
While you could probably get more money for the grille that's currently on the car, you'd have the hassle of changing out the grilles, plus you'd need to repair the original grille, so you'll lose the extra money in getting it fixed. Unless you could do it yourself, in which case why not just fix it and sell that one?
