I would look at IntelliChoice
http://www.intellichoice.com/ic2/ which lets you enter a model car and determine operating expenses - both the 95 w124 wagon and the 95 940 Volvo wagon rate as excellent. I would also check
http://www.nhtsa.dot.gov/cars/problems/tsb/servicemmy1.cfm for the problems/technical service bulletins to see what kind of obvious problems the cars have. The 95 MB had 1 (instrument cluster), the 95 940 had 5 (3AC, electrical, seat track). Useful starting points IMHO. Good luck on the search.
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John
2003 Firemist Red/grey leather SL 500
2015 Palladium Silver/black mbtex GLK 350
1987 Smoke Silver/burgundy mbtex 300E Sportline (SOLD)
Click to see 87 300E