If you were living in Europe, the only possible good purchase to make is the W107 SL (6-cylinder preferred).
All the other cars you mentioned are doomed to cost you money instead of bringing any.
The W123 is only good as a coupe (we own a "80 230CE ourselves since yesterday), all the sedans don't do anything reasonable here. SE and SEL's (W126) can hardly be sold here.
But then again, that is in Europe. If I were you, I would buy me a SL and enjoy some roofless rides in sunny weather!
with a minor 600+k