1st- the 190's are pretty small, so if you have children or often rear passangers, very tall person, etc. you might want to think twice, but if this is not applicable, read to #2.
2nd- another place to look out for rust is where the battery compartment is, and along the firewall, when wet leaves get into there and cause dampness, it can rust there.
3rd- I would go for the 1992. The later models seem to be better to me. You didnt go into detail about each one of them, so its hard to say. The later models seemed to be more trouble free than the earlier ones.
4th- are the AC systems converted to R134A? I have had a lot of AC problems and auxillary fan problems with the 190 i had. If it works, then this isnt applicable, but if its not converted, you might get some negotiating power.
I cant think of anything else right now, too early in the morning, lol.