I assume its an 80 series Landcruiser you have, here's a bit of info from offroad.com...
80 Series Specific Info
Full time 4wd
All 80 series Cruisers sold in North America and Europe are full time 4wd. In Africa and Australia, a part-time system is still available. 80's produced between '90-'91 have an open center differential which is lockable in 4HI and automatically locked in 4LO. From '92 on, vehicles with ABS had a viscous coupling that sent a maximum of 30% torque the non-slipping axle. The differential is lockable in 4HI and automatically locked in 4LO.
Locking Differentials
Locking differentials were available as options in all 80 series. From 94 on, they were standard in North America. The operation of the lockers is very elegant. When the differential lock dial is turned to the "Locked" position, it switches on a small electrical servo. The servo pushes on a dog clutch which is meshed with the splines on the axle shaft. The dog clutch slides along the axle shaft and engages on the side of the differential carrier. The axle is then completely locked. They were offered from the procuction date 8/92 onwards.
You can also try
www.tlca.org, although their website is down right now. Haven't visited TLCA for a while, so I'm not sure how long their site has been down...
As for parts, you can try Specter off-road for non-American performance parts, they mainly show older LC parts, but have stuff for 80 series too.
http://www.sor.com/
Congrats on the new vehicle!