The front of a 120 is not flat (nor is a 140 I guess), unless you want your lights pointing off to the side (like cornering lights on a rally car), I would think that the holes should be oblong....

When I first read this post a few weeks ago I thought that you had meant only a bracket "mounting through the grille" (hovering lights look) which is pretty cool too, and simple with an L bracket and some fender washers. Seeing where this thread has gone, however, I am a bit disappointed, but only because I thought that I had had an original idea. :^] Turns out there is no such thing.

Compromising airflow? Most of the grille is for looks, 50% of what is behind each grille is not the radiator.