The ones with the LSD will say "LSD oil only" on the rear differential casing.
Just bear in mind that the LSD (clutch-type) has a really low torque spec and is not very useful.
The best advice I can give you is make sure that you don't pay too much for your used X. I see people selling them way over
book value all of the time. Just don't rush and get the right one at the right price.
Regardless of what year or trim level you select, it should be a fun and versatile vehicle.
Good luck!