The extended beak portion of the urethane nose on the 73 is little different than the 70-72 nose. And the grill inserts are different as well, they don't fit flush to the opening and sit a couple inches back. The hood latch is also under the bumper on a 73 versus in the driver's side grill insert on a 70-72. All this had to do with the new for 1973 5-mph bumper laws. There is also about 50 pounds of extra steel bracing behind the nose piece on a 73. A 70-72 nose cone won't be that hard to find. Easier than finding a 73.
Post some underhood shots and I can tell you if they replaced the fenders as well.
Here's a 72, notice how the grills extend to the opening? Also, every year had a different grill insert with a different grate texture - 72 had the honeycomb grills.
