I wouldn't worry about the miles. The history of the car is more important. I've had better luck with hi-mile Benz's than lower mile ones, but I know what to look for in a 123,124 & 126.
The only thing I know about 140 chassis is the can be real money pits. You need to look beyond the purchase price and figure at least $2-3K a year in maintainance. If you can handle that, it's an AWSOME car. Do a search on 140 chassis.
Or you could see if you can get a deal on a used Space Shuttle, they're cheaper to maintain and less complicated
91 300E 120K
90 300SE 275K (sold)
92 BMW 525iM 120K
90 BMW 525iA 175K
85 300D 175K (sold)
84 300SD 245K (sold)