I can answer this. On the outside yes, the outer layer is the same, but the part around the headlight bucket and inside edge is different, there are additional tabs to mount the 65 grille and headlight trim. You could cut up one to piece together the other but it is not a direct replacement - well, you can mount it but you won't be able to mount the headlights or grille.
I found this on a 65 where someone had mounted a 64 fender, and that explained why they never put the grille back on after that.
