If they are not broke, don't mess with 'em.
The rear axle bearings will probably last you the rest of your life, and whoever has the vehicle after you...
The fronts, if the grease seal is not leaking, and there is no excessive play in the hub/wheel assembly, I would not think about doing anything with them, until you are in there doing something else. That certainly goes the same for the rear axle wheel bearings.
If your truck is not leaking oil or grease, goes down the road fine for a 30+ year old vehicle, and you are not going to be tearing the whole truck apart for a frame up restoration, I would not worry about things, until something shows you a sign that it needs attention, unless, you REALLY want to start throwing money and time at the truck...
Grease all the zerks; get a good grease gun, pistol style that accepts a full size cartridge.
I would drive it, learn about it and how it functions, become familiar with the idiosyncrasies that all Land Cruisers posses, and go from there. Get a base line established, so that you know what your truck runs and sounds like. This will help you in the future when you are trying to diagnose something that seems ami
Good luck!
-Steve