This isn't a very good picture, but you'll be looking for a thin metal tag on the left side of the rear diff cover, behind the left axle flange:
http://www.nmia.com/~dgnrg/diff2.jpg
If if has an "S" prefix on the tag, followed by numbers such as 3,15 then it has LSD. As long as you have it raised to check for the tag, spin one of the wheels and if they both rotate in the same direction, then it has LSD. If they rotate in opposite directions, the it's not LSD. You can also check for LSD by raising only one wheel leaving the other on the ground, with the front wheels chocked, and the gear in neutral with the brake released. If the wheel does not rotate, it's LSD, if it rotates freely, then it's not LSD.