If you go and lurk over in the Diesel section, there are several that are scared of the 3B, 13B-T, 2H, 12H-T, etc. because they are no longer in production and have been replaced by the 1HZ, HD-T, 15B-T, etc. which are still currently being produced. (disclaimer: I don't own a Toyota diesel so I don't know firsthand any of this, but this is what I've heard so you may want to look into it) Some parts are already supposedly becoming scarce for the 3B etc. from Toyota, so some say that if you're considering a motor replacement/diesel swap to look at current production engines because parts will be available for a long long time from now. A 3B was stock for BJ42s and 13B-T fits pretty well into an FJ40/BJ42 because it's a very similar engine (and there are many examples of both on this site), but some guys have done 1HZ/1HD-T swaps as well, which seem to be a little more of a shoehorn to get everything to fit up right (but again there are some swap threads on this site you can take a look at). crushers, rutbeer, JABXYZ and some others come to mind for some of the various swaps.
But back to the basic premise of your thread: I have to tell you from my few years owning and operating vehicles (I'm only 25), I have found it to be a LOT less stressful for me to own and DD a newer model vehicle (a 2000 Tundra), which is basically completely stock, that I can depend to get me to and from work. My FJ40 is my toy. Yes I keep it so I can pretty much drive it anywhere in the world at the drop of a hat, but since it's 34 years old this year it continues to show its age. Stuff breaks down or stops working randomly. Nothing is up to the standards of modern vehicles (suspension, lights, heater, wipers, cab noise, safety restraints, fuel economy, parts availability, mechanics who can diagnose and work on it, etc.) - that's fine on a toy, but I have found it's not ok on a DD (for me). I have MUCH more peace of mind knowing that if something stops working on my FJ40 I can park it until I can get it fixed and have some other means of getting around. I have been in the place where my FJ40 was my DD for a time and I had a major mechanical issue come up in the middle of it and I was left trying to come up with an alternate form of transportation.
To me, that situation is further exacerbated by your notion of putting in a non-USA engine in a 30-40 year old vehicle. Nobody is going to be able to work on it except for you. Parts may be hard to find - either they are being discontinued (3B etc.) or never made it to the main markets in USA/Canada (1HZ, 1HD-T, etc.). If you really must have a Land Cruiser as your DD, get a 100% stock FJ40, or even better an FJ60/62, FZJ80 or 100 series (all stock and well-maintained to ensure reliability, maintainability and serviceability) and then have your diesel converted FJ40 as your toy. The 40 series trucks aren't getting any newer, and you're going to also have to consider all the other things that wear out over time that you'll have to keep on top of if you're going to have a reasonably vehicle to DD (seats, weatherstripping, wiring connections, RUST, seals, gaskets, tranny, diffs, spring bushings, etc.)
That's my two cents.