Gotta agree with Squabble to some extent. Don't buy a perfect example and plan on running wvo through it. I don't imply that you haven't read how to do it the right way. Just that the resale value of a wvo car will never be as high as one that has been untampered with.
A 200k mile sedan should never go for anywhere near 6k. A wagon or coupe in near mint condition could go for that much with 200k, but never a sedan.
For 4k, you should be able to buy one with working a/c, extensive service records and some major maintenance items already done (ie. rear axles, front end rebuild, a/c rebuild, etc). Florida has a glut of these cars without rust in good condition. A good service history is more important than miles. And while cosmetics can get expensive, its much better to buy a car in great mechanical shape and a few niggling cosmetic issues than one that looks great but has some mechanical problems on the horizon.

There's lots of threads detailing what to look for, but being in Florida, make sure the car has remained a southern car. Rust is one of the few things that 'kill' a W123. Better to have to replace an engine than deal with a car with serious floor pan rust. ANY rust you can see plainly is the tip of the iceberg.

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