The grills are 73 and if they fit that bumper correctly then the bumpers a 73. It can be used but there aren't any repro grills or chrome bezels available yet that I know of. The most noticable difference appearance wise is that the nose sticks out farther. I believe they changed it for 73 to meet new impact regulations. You can see the difference in the pic below of the white 73 and my 70 behind.
