Time to resurrect this thread.
I've got a 1970 K, and want to put windows in the lower half of the doors.
It looks like I can de-rivet where the stiffener attaches to the skin, cut the hole in skin, put the Plexiglas between the stiffener and the "window frame" portion of the skin, then just re-rivet.
Having been in a Patroller, I can tell you that just the square foot or so of window really makes a difference in visibility to the sides and down.
