The original Kasiner extrusions, which may be available from OK, would work. You would need to belt-sand the corrugations off above the windows. Get him to punch windows, then sand the corrugations off yourself. Easy.
I think I would be tempted to use ends and trucks, and interiors as well, from cannibalized K-Line or MTH.
I am really glad I have no real info on passenger car window arrangements. I have a lot of K-Line, and while I am quite sure some of the windows are incorrect, I do not carry a "spotter's guide" with me when I run them, or even look at them. I sure do spot incorrect car bodies, though. The one you want has never really been done to perfection in O Scale, to my knowledge.
