I've done a few 64' Plymouth grilles, and even attempted the single headlight conversion on one.
If you look at the grille in the pic, you can see the cut line. The owner and I agreed that it would look soooo much better if it could be done without seeing a cut line. So I proceeded on that route. Without a car here to mock it up, I made a graph on my garage floor and went at it. That damn thing fought me the whole way, even kicked my azz!!!! While I did manage to get it done without a cut line showing, it was total garbage in my opinion. The owner of that grille new way ahead of time that without a car to mock it against, I was shooting in the dark with my eye closed. So after 3 months of working on it, I had to send it back to him.
I would do another, but not without the car being here so I can check, double check, re-check, then check it again. A 64' Dodge is cake, but I have stuff here to check the fitment of the grille.