Clayton,
I gather you're speaking not from driving a Mercedes diesel, but from seeing soot-covered, smoke-belching, worn-out VWs, and the rumors of an attempted class-action lawsuit against Mercedes for ONE particularly terrible engine they produced in the mid-eighties that routinely died around 80k miles due to cylinder wear & block warpage. (Granted that's fine by GM's standards...) ONE badly engineered motor in the last half century (or better). Give them some credit! In general they're wonderful motors, reliable as any red block Volvo, clean-burning, efficient and pleasant to drive, albeit a completely different feel than a gas engine (flooring the accelerator? No! - use some finesse & roll into the throttle instead). I must respectfully disagree with you here.
On the matter of practicality, however, I'd say don't bother with it unless you have a Mercedes to dismantle and plenty of time to make it fit (and if you've got a good diesel Mercedes, why not just drive it?). The Volvo diesel is a VW, same motor as the old Golf/Jetta 1.6 diesel, but with 2 extra (and poorly cooled/lubricated) cylinders tacked on either end. It's not a truly bad motor, nice for long haul highway driving but it really pales in comparison to Mercedes for longevity and it's very maintenance-intensive. And good luck finding a decent diesel mechanic to work on it!
--
Chris, Dartmouth NS Canada 70 M-B 280SE, 83 245DL, 84 244 turbo, 90 780 turbo, 92 VW Golf