Good morning! Just ran across this thread and thought I'd share some experiences. As far as the VW mill goes, they last a long time and have good power if they're turboed, but not much torque, and they're a high winder. There is a co. that makes conversion kits for these mills in the Samarai ... I'd love to do one of these in my spare time later if I can find a clean Zuki.
Now for direct experience. I've run Benz OM617 5 cyls for years and you almost can't tear 'em up. My latest swap is in one of my IH Scout II's. It's a weird duck, but fun none the less. It's a right hand drive w/half cab. The benz motor looks like a factory install. I have a homebrew propan system on it and with 31-10.50 mudders, I can brakestand a smokestorm with it.
These engines are awesome and with a little free tweeking run awesome. I've actually been looking for a clean Durango with a puked motor just to do another conversion! I think this would be an ultimate mid size ride!
Quigly
The pic is one before is was completed, but shows how the benz rad & oil cooler fit right into the stock IH core support.