There are several aspects to this conversation that are important:
This section covers two aspects of potentially having a diesel powered truck: 

1) Doing a industrial diesel conversion like a Cummins Conversion.
2) A factory diesel powered truck or a conversion (otherwise known as a "repower") into a Land Cruiser with deemed "suitable" for an automotive application by the Toyota factory.  This means putting a Toyota diesel into a Land Cruiser.

What is is like to own a diesel is a question that is important to consider.  A few weeks ago on the Land Cruiser Mailing List, I remember a conversation regarding "what engine does the Land Cruiser guru Mark Whatley run?" - Mark is the Technical Editor of Toyota Trails Magazine, and, in my opinion perhaps one of the most people about Land Cruiser gasoline engines in the world.  Mark wrote back:

"I don't have anything against a well thought out engine swap. I don't
think that I can argue real hard for or against one. So long as you
understand the strengths and weaknesses of whatever powerplant you are
contemplating installing, and you are honest with yourself about how you
will be using the rig and what it will end up costing you"

Personally I think this is great piece of advice because there are strengths and weaknesses to all conversions, especially diesel conversions.  You might want to check out this page on costs of a diesel engine conversion.  Here are my thoughts:

Regarding an industrial / commercial diesel engine transplant into a Land Cruiser or other vehicle: Personally, for me the bottom line is I've never owned an industrial /commercial diesel engine and have never had one in a Land Cruiser.  For example, the Cummins 4BT was never available in an automobile other than super rare factory Cummins 4BT powered Dodge Dakota small pickup trucks for government use.  The Cummins 6BT, bottom line, is an industrail grade / commercial engine that is more than powerful enough to power a large motor home and/or industrial sized truck.  However, luckily for diesel enthusiasts, is it available in Dodge pickup trucks as well.

Because of the recent trend in the American automotive market to put large, very powerful diesels into full size pickup trucks, the idea has been going around that diesels like this are suitable for automotive applications like a Land Cruiser.

The bottom line is there are aspects to owning a diesel that are no where near the same as a gas engine.  In some applications there is not a major difference and lot of it has to do with what you plan to do with your truck and where you live, and of course, how much you want to spend.

Can you put a Cummins in a FJ62 and expect it to be your daily driver for your and your family?  Honestly I'm not sure but I would expect your familar to have to be "pretty tough" to deal with the noise, added height and weight of the truck, stench, and lack of available fuel in remote locations.  Of course there are other factors too.

Purchasing a Factory Toyota Diesel
Purchasing a factory Toyota diesel is actually a whole different ball game in my opinion.  Factory Toyota diesels found in automotive applications are actually totally different and could be considered significantly more like gas engines.  they have higher horsepower and less torque, are generally quieter, and run smoother.  For example, my 2H powered Canadian Spec HJ60 actually redlines higher than a USA spec gas powered FJ60 with a 2F engine, has a 5th gear that was never available in the USA, and is quiet when idling though of course you can still tell it is a diesel.  But diesels do drive differently.  If it's a V8 you want then you should actually get a V8. Diesel engines lack horsepower.

However, diesel engines do have plenty of torque.  In fact I believe in 4 wheel drive applications, torque is a lot more important than horsepower.  But for all around daily drivers it is worth it to have the horsepower, to be able to fly up a hill, and to have the truck generally feel all around powerful, the way you would like it to.  Diesel Engines only real advantage is milage in an automotive application. Otherwise, it is a dirty and stinky fuel when you refill, and smells on all ends, at the exhaust pipe and at the pump.

Furthermore, Driving a diesel truck can become a proactive activity when driving,, not an inactive activity like most daily driving usually is.  You must have the time and energy to make basic maintenance items.  You should install a EGT gauge to be aware of your combustion temperatures, if they are not watched and if the engine is not tuned properly you can do damage to your engine.  With a turbo charged model after driving, you have to wait a few minutes to allow it to cool down every time you turn it off.

Factory Toyota diesels are actually a good bet in my opinion, particularly non-turbo charged versions which is why I believe Toyota still manuifactures non-turbo charged versions.  You do not have to wait for the turbo to cool down when turning off the truck.  A factory Toyota diesel is incredibly easy to daily drive.  They are designed more like gas powered cruisers with the added benefit of diesel efficency (and some quirks which you may or may not like) but in the end they are not simple like gassers. 

But finding rare non-USA parts can be tedious and expensive.  In a non-USA spec diesel you'll spend upwards of $30 in oil and filter alone to simply change the engine oil.  Diesel engine oil is also nasty.  It is always bright black and stinky.  If you get it on your hands it will dye your hands black, simply the nature of diesel engine oil.  Plus, most diesel take in excess of 10 quarter per oil change.   The engine compartment can also be black and stinky (though sometimes it will be clean if you are lucky).   In winter you should plug them in.  If you don't they will not last.  But, a well taken care of diesel will last you easily as long as your Land Cruiser will.  If you do not have rust, this could be for dozens of years.

These are all things to consider.  Plus, I am positive there are better applications for diesel conversions other than expensive non-USA Toyotas and rough American Cummins diesels - other than the Cummins 6AT which is actually a lot like a mild mannered Toyota Diesel.