1973 didn't use the filler IIRC. That began in 1974 with the shock absorber front bumpers. The 73 I bought new back in the day did not have them. My current 1974 Duster without shock mount front bumpers doesn't have them either.
Hmm that’s odd. Because if you look at the pic of my car above I am clearly missing something under the grill but above the front bumper. Maybe I’m calling it the wrong name? Anyone know what that part is called???