Yes, it is a longer wheelbase for models with the "L" in the model designation. The thing is, the 300SDL also has a six cylinder engine which is longer than the OM617, once mounted, the transmission may very well sit farther back in the chassis which will mean that even the original drive shaft for the swb w126 could be too long. The only other issue I do not know about concerns the transmission output shaft. Could it be different from the transmission that comes with the OM617? Even so, couldn't that be unbolted from the front of the drive shaft from the 300SDL car and used instead? Seems like a possibility. So that would leave one with the possible issue that the drive shaft would be too long. And I believe a drive shaft shop could shorten it relatively easily and cheaply.

There's also the possibility of finding a drive shaft from a 350SD donor as these had the six cylinder and they are also short wheel base cars. Which brings me back to the other issue I do not know about concerns the transmission output shaft. Could it be different from the transmission that comes with the OM617? Even so, couldn't that be unbolted from the front of the drive shaft from the 350SD car and used instead? Seems like a possibility.

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Dedicated to the preservation of antique Mercedes Benz's, one rusty ol' bucket of bolts at a time!

So a 300SD with ABS?! How cool is that! It would also have the high gear ratio diff too, what is that 2:88's, right? That's just too cool to pass up for free! Looks like the color of the interior is cream? That's a great color and pretty rare too I think. I know of a 2nd gen car just came into a local PnP with cream color interior with some great seats (which they sell real cheap)...

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Dedicated to the preservation of antique Mercedes Benz's, one rusty ol' bucket of bolts at a time!

Yes, for 1985 ABS and airbags were optional on all W126s. It should have the 2.88 diff and the high stall speed converter, as well as the vacuum amplifier for boost compensation