Switching the two seats is definitely not possible, but switching the backrests only might be (I didn't read the post well enough last night/morning).
It depends on the location of the backrest adjusting motor and cogles whether you can exchange them or not. It is not a problem for the headrest adjusting or the possible heated seats option, but it depends on the location of the adjusting devices.

greetingz,

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1990 300SL-24
1993 C250D with a minor 600+k kilometer
www.MBenzNL.com(the Netherlands)