I did a little checking today--I compared a male 163-type receptacle
with a C14 receptacle. The mounting ear holes appear to have the same
spacing; the C14 is about 3/4" thick, where the 163 (metal shell) is
about 1/2" thickness, so you'd need to enlarge the mounting holes about
1/8" on the top and bottom. The 163 is a bit wider, but not enough to
matter--you'll have to square off the hole corners, as the shell of a
163 is oval, not rectangular.
All in all, if done carefully, there's no indication that anyone could
tell if a modification had been made.
Since a lot of my stuff runs from C13-equipped power strips, is it
possible to get a ready-made line cord with a C14 on one end and a C5 or
C7 on the other?
--Chuck