You CAN use the 73 fenders, it just takes a little fabrication to do it.

If I remember, the 73-76 fenders used a small piece below the grille that was held in by (2) phillips head screws that mated up to the different style lower grille panel.

Take those off (if they're on the fender), & the lower holes will be in the same place as on your 72 fenders.

You'll need to make, or take the brackets off of your fenders that hold the upper grille panel to the fender.