If you have a truck with a 22R in it, the easiest swap is to a Toyota 'L' series engine. The best option there in engines available in the US would be a 2L-T. You could convert it to a 2L-TE pretty easily I believe and that might be worthwhile. This is a nice option because the motor mount locations for the 22R and 2L are the same, you just need to source the rubber isolators (should be in the North American parts system) and no need to move the frame side of the motor mounts or the tranny mount.
You need to source the whole drivetrain, the bellhousings are not the same. But you can keep your current tranny (most likely) and transfer. You'll need the engine wiring harness, fuel tank, fuel lines and all of that from the diesel truck. But no need to re-work driveshafts or anything with a 2L. This option, if you find a donor truck, will be the cheapest route. Finding a donor is tough, there aren't many of them in the US.
The next option would be to get a half cut from Jarco. This is essentially the front half (minus the roof) of a Japanese car. They run about $5,000 for a 2L-TE Hilux. The regular 2L is like a 22R running on 2 cylinders, pretty pathetic on the US highways. The turbo helped, but the turbos on these engines are not known for being particularly reliable and they are expensive to rebuild.
So you might want to go with a different engine, which will require moving the drivetrain and re-welding motor mounts. In that case, a 1KZ-TE is supposed to be a much nicer engine. Best option here is a half cut and they run about $6,500. You definitely need a half cut because we never got a factory vehicle with a 1KZ-TE and so there are zero parts available through your local dealer and trying to find all the little this and that parts will be impossible and waiting 2 weeks each time you need a connector, bracket or a bolt for it to come from Australia or Japan will be a huge PITA.
Next option is going to a different engine, a US-available VW TDi, Mercedes, Cummins, etc. This is completely custom work and you might or might not be able to keep the Toyota drivetrain, depending on what Advance Adapters or other engine-to-tranny adapters are out there. Expect this route to be significantly more money and effort, but probably not too much worse than a 1KZ-TE swap. The main advantage to the 1KZ is that there are factory bellhousings that will mate with your W56, so the half cut route saves you from needing a third party adapter. Also the engine was designed to fit in your style truck, so the oil pan clears the front axle, the linkages and wires fit the engine bay, etc. With a non-Toyota diesel these things are not impossible to overcome, but just keep popping up.
When my engine died a year ago, I looked into the 2L-TE route. There were none immediately available for a manual tranny (you have to get the half cut that matches your tranny to get the right bellhousing). It was also gonna be tough to get a less than 25 year old truck (mine's a 1991) approved by the State of Colorado for the diesel conversion since it's titled as a gas engine truck. Laws are different in different places and if I did not live in place where we have emissions laws it might have been different. It was gonna be about $5,000 in parts, $500 to ship half a car to my house and then you still have to convert the engine harness from right hand drive to left, essentially removing all the bundles and re-bundling the harness. Lots of work, there is a reason why a turn-key diesel conversion is usually around $10,000. But if I valued my labor at zero dollars, it was still going to be at least twice as much to put in a used diesel as I spent to put in an essentially brand new 22R-E.
Given that at the time diesel was the same price as gas, I figured to come close to working out economically I would have to get at least a 10 MPG increase in fuel economy (probably on the high side of optimistically reasonable) and it would have to last at least another 100,000 miles before needing any significant work. This on an engine that would not be new and probably have about 75,000 to 100,000 miles on it already. If the turbo died before 200,000 miles, that would essentially make it a money loser. I stuck with the 22R-E and my new engine has been giving me about 2 MPG better than I used as the basis for my cost estimates and diesel is not a 20% premium over gasoline.
