What Diesel should I put in a G-Wagen?

[llaskin]

If the characteristics I want in a MB engine are the following, which engine should I put in my G-Wagen?:
-Longevity
-Reliability (perhaps this means getting a naturally aspirated over a turbo? Turbos have more electronics.
-Fuel efficiency. (I don't really care that much about power. However, this doesn't necessarily mean I want a small engine. Many of the older small engines aren't that efficent).[B]Longevity