While I had my driveshaft out, I pulled my front flex disc from my 1993 300D because I could feel some backlash when twisting the shaft in Park.
The disc has no cracking and looks and feels solid. Genuine Mercedes disc. But the holes seem maybe slightly ovaled and the metal sleeves can be spun in their holes.

I have a new disc I ordered, Febi with "Made in Germany" markings. The sleeves cannot be moved at all relative to the disc.
I was going to just change the disc while I had the driveshaft out. But everyone talks about cracking and cords, not the sleeves coming loose. Is this early or late stage wear?
Will my new disc will soon look like this after 10k miles, and I should save it for later? It's really not that big of a pain to get under there and change it, after all.

I've not noticed sleeves being loose or tight, but the backlash is what softens and cushions the varying torsion in the driveline, that is why the front/back orientation matters i.e., so the movement in the disc is the right orientation to absorb the shock. The sleeves position the disc in the driveshaft and the transmission output flange and they prevent the crushing of the disc when the bolts are tightened. If it looks good I'd use it.

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Thanks, I've reinstalled the driveshaft and stored away the new disc as a spare. With the new center support bearing and rubber mount, the amount of backlash feels "more acceptable" since the whole driveline is not flopping around.

I'll order a rear disc to set aside with it, as the rear has a few cracks in it though it feels rock solid. Definitely very different from the front disc.

I reinstalled the discs with reused hardware and blue loctite as I have seen recommended.

Order shifter bushings and a driveshaft centering bushing too. If you're keeping it forever consider another center support if they aren't too expensive.

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

I've barely owned the car so far, bought it cheap with the center support blown and the turbo not making any boost (vacuum line snapped off ) but the interior is in beautiful shape and there's only a bit of rust on the body.

Planning to drive for a couple months and see if any other gremlins pop up before I start stocking extra flex discs, center supports etc. but I'm hoping to get the rust fixed and make this a long term daily driver.

Shifter bushings are a good idea as they looked pretty worn when I was under there. Driveshaft bushings were in good shape, I cleaned and added moly as specified in the manual, but they are likely cheap to have on the shelf as well.

Things like the shifter bushings I'm usually printing in TPU on the fly these days if I pull something apart and find a rubber parts surprise. It's a remarkably tough material, as long as it doesn't get too hot!