I have always used original M.B. shocks on my cars, but I believe Bilstein manufactures those for M.B. anyway, so any aftermarket Bilstein that fits your car would be O.K., I guess.
One important fact: shocks must always be changed in pairs, if you change the left rear shock, the right one must also be changed. This is done to keep handling characteristics right.
S 320, 1998
E 320 T, 1995