The stuff that I was talking about is the Gen III Vortech V8s used in the GM trucks. Its work but it can be done and there is an adapter to allow the use of the LT230 behind a GM transmission. Swap it in with the transmission, motor and gas pedal (drive by wire) and youve all you need. It wont be easy but they do get great mileage for the power thats there. As for V6's, and V8 prior to the new Gen III V8s and the Vortech 4.3 V6, will bolt to the stock ZF auto transmission with a readily available adapter.
You would need to drive a LOT of miles in a few years to pay for the cost of the drivetrain, the cost of the install and the increased cost in fuel as diesel is more than midgrade per gallon. Here, its 3.06/ gal for diesel and 2.78/ gal for midgrade (what I run). Like I said, youre going to have to REALLY want a diesel to do the swap. I seriously was going to do it. Lined up a Disco swap "kit" and a shop to do it. Then, while driving my dads GMC around, started thinking about how a gasser would be easier and much cheaper and net me a few more mpg/ increased range, and the left over difference between a diesel and gas install will buy a lot of gas. Gas will always be cheaper than diesel. Sure, I could run waste veggie oil in it if it were diesel but I have no place to refine/ filter the oil and there is no place to buy it so thats not even an attractive option.