I finally decided to do something historical, instead of stuff for my AU, just because it was simple and easy to do:
North Korean Cessna 172
Apparently they have been making them over there (undoubtedly unlicensed) and there are a few differences, mainly internal, but nothing external that was noticeable enough to warrant a change of the drawing. Kim Jong Un reportedly flew one the same as the bottom one a while back. And there were no serial numbers on the things, I haven't just left a gap and not applied them.