Found out my XJ has a rear limitied slip differential and wonder if that is the same as a locker? Would it be best to install a front locker? Did they make front axles with lsd?

 

I think the arguement for front or rear locker first is a 49/50 split (with a slight rear locker preference bias)
LSD is not a full locker by any means. but I was told that you can engage it more efficiently by pulling the e-brake back a few clicks? then gassing it
but yeah I think most will agree that if you already have LSD rear, you should lock the front
in the case of having a rear D35, definitely lock the front