W209 shared parts?
Means i can install w203 headlamps or w211 tail lamps on the w209?
The clk200k engine is shared with the e200k as well?


I'd say most of the exterior parts are not shared, except may be w209/w203 side mirrors, and maybe front elements (fenders, bumper) for c55 (c55 front end is different to the rest of w203s). Mechanically w203 and w209 are very close. I know that with w211 clk shares some interior parts like steering wheel, dash.
And yes, engines are also interchangeable, technically you can put engine from w211 into w209, but I'm not sure that you can put v8s into regular w203.


