You get quite good at cross referencing the parts fiches. Toyota, for the most part, did quite a good job not re-tooling for every model, using parts on the same year of different models of Land Cruiser.
Yes, some parts are difficult to find, but I have yet to find anything that's impossible...of course when a part hits the "unobtanium" scale, the price goes up accordingly. For instance, a 40/45 series brake booster...so many times a more common item, in my example a booster from a 60 series, can be made to work just fine.
IH8MUD is an excellent source for used parts, and I have found some from cruiserparts.net as well.
-H-