[DieselSJ]

Hassle is an ambiguous term.

You didn't mention what trans. You will need an overdrive if you want any economy at all.

6.2/6.5 will bolt in...literally. But you have engine age, and the 6.5 turbo setup won't fit with factory heater box in the engine compartment. Parts are getting harder to find, but they are out there. Avoid the electronically controlled engines.

Duramax (6.6) you can find engine mounts now from several sources. You need to be good at wiring or spend $$$ on a stand-alone harness. Used engines are coming down in price, but you are still going to spend 4-5-6K on just an engine.

Cummins. Big, heavy, can find bolt-in mounts. Easy to wire. Need to adapt GM to Dodge for accessories, etc... Look in the diesel conversion sub forum and you will find several of these. This will probably take the most fabrication.

That being said, I stuffed a 6.5 turbo into my Jeep Grand Wagoneer and have it built into a 275hp/550tq piece. Backed by a 700R4 that was built on a K case and has every possible upgrade installed. If I had to do it again, it would get a 4bt because of what it just cost to build a new 6.5 for it.

And my 87 R30 (currently 454) is going to see a Cummins some day.

One thing you didn't tell us was how you intend to use the truck? Heavy duty tow rig, well then Cummins or Duramax or get really cool and use an International DT360. If you have a half ton that you want to cruise around with and do some light duty towing, then stuff in a Cummins 4bt.