Grille question

Both DusterKrazy and zkx14 are correct. The 75-76 grille, filler panel, and headlight bezels are different.
The metal filler panel has holes where the plastic filler screws into it because of the bumper shocks and also has extra metal to account for the recessed turn signals, and because the signals are recessed, the headlight bezels are longer ( deeper ) on the grille side.
The other thing to consider if you are going to convert and remove the plastic bumper filler piece is that you'll need to drill out the bumper shock mounts and collapse them and you'll need the little "end" pieces that go on the front fender just to the sides of the 73-74 lower bumper filler....goofy little things that get lost really easy. Not a straight up of a swap as you might think just to swap a grille