Grille swap Q's

I have a '73 fastback (non Mach I), and my grille needs replacement. I have always liked the '71 to '72 Mach I grilles, and would like to put one on my '73. Is this a direct, bolt on swap, or are the mounting points different due to the changes required to accomodate the larger bumper on the '73? I know I can swap in a '73 Mach I grille, but I prefer the look of the '71. any help is appreciated.
Thanks in advance.
 
The primary issue with attempting to use a 71-2 Mach 1 grille on a 73 is, the full length protruding plastic lip on the bottom of the 71-2 grille will interfere with your 73 urethane bumper. The second issue is, the hole in the top of the 71-2 grille for the hood release latch would have to be relocated/enlarged. Headlight mounting bucket points are the same for all and I’m sure any center support mounting issues could be gracefully overcome, but given the first 2 issues, I wouldn’t attempt it.

I’m not a big fan of the understated look of the 73 Mach 1 grille, so I plan on installing the standard 73 grille (with the large horse in the corral) on my 73 Mach 1.
 
Thanks,
Yeah I wondered about the lower "lip" on the earlier grilles. I read elsewhere that to do it right, almost need a donor car's front end and swap the fenders, radiator supports, lower valence, bumper, and the hood latch release. Guess I'll stick to the '73 grilles. Now to decide if to keep the original look of the egg crate grille, or the Mach I grille... maybe custom billet alum inserts? :D