I've always loved the front end of the W126 SEC coupe...and I have seen a local W126 sedan that has a coupe hood and headlights. O_O I was just wondering if this is a plug-and-play swap of parts, or if the conversion requires more modification?

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Current cars:
2000 ML55 AMG, 174k miles
2003 C240 T-Modell, 202k miles
1995 S320, 207k Miles

I did this to my car... have a look in the gallery.

No, its not quite as easy as just swapping in the coupe parts, a little cutting and welding is needed.

The bare minimum you need to cut out and replace by welding is the entire hood slam panel ie. from fender to fender, not just the central part above the radiator. For a true conversion, the inner fenders also need changing, although the only difference is the very frontmost fender mounting hole won't line up and needs leaving out.

Other than that, you need the hood, fenders, bumper, headlights, turn signals.
The existing AC condenser does fit, but the mounts for the clips are in the wrong place, so it just relies on being clamped in by the engine radator. So again, for a true conversion, you need the SEC condenser too.

By true, I mean seamless, how Mercedes would have done it in the factory.

Cheers,
Ben.