I have a pair of black coupe seats from a 300CD. I would say they are excellent, in terms of the quality of the Tex and the support. It's an 1981, so either this car was babied, or the seats were replaced at some point. The folding forward mechanism works well on both.

The one problem with both seats is that I had to cut out the rear bolts to remove them from the parts car. The fronts bolts were fine, and the seat is still attached to the rails. But the rear bolts were rusted to the floorboards, so I had to get out the Dremel. If your original rail assemblies are in good shape, you can easily reuse them. It's pretty straightforward to swap rail assemblies between seats.

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-1985 300TD - 324k mi on chassis. MB "Tauschaggregat" 617 motor + 4-speed conversion
Alaska Roadtrip 2009
-2002 E320 Wagon - 197k mi
-1998 E320 Wagon - 310k mi - retired