Sure, a 240's 4-speed manual would work, fabbing a driveshaft wouldn't be any more difficult for a 126 than a 123 and, it might just be possible to find a manual-equipped gasser Euro W126 to donate a pedal assembly for such a project. However, as BHD has mentioned, the 126 has an electrically powered speedo and I know for a fact that the speedo drive in the tailhousings are not interchangeable between auto and manual.

But, the turbo 617 is ungoverned between 1100rpm and max revs making for some strange and unpredicable shifting. Personally, I think something that is so unequivocally a luxury vehicle like the 126, really isn't a candidate for a manual tranny. The 603 engine does seem to be governed and may actually be a better candidate for a project like this.

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Never a dull moment at Berry Hill Farm.