You're not going to find any big Benz with a manual gearbox in the U.S. I know I have sean pictures in the factory manual for a W116 that showed a manual tranny. So they did exist, but not here. Your big problem is getting a manual tranny from Europe.

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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member