Once you stop the clutch from spinning, you can just use an ordinary 8mm L-type hex key wrench to remove the center bolt.
Put a 1 ft (or so) length of 3/8 steel pipe on it for extra leverage.
No special tool required this way.
Tough to get a hex-key socket in there, and that radiator is fragile (and expen$ive).

I also cut my fan shroud at 9:00 and 3:00 so that it can be removed with the fan on. Re-attached the 2 sections with zip-ties.
Not pretty, but saves a lot of trouble anytime you want to access the front of the engine...

Best of luck, and happy wrenching.

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1986 300E 5-Speed 240k mi.