You don't really have to use new shocks with a 2" lift, but I'd highly reccomend it.
I've found that YJ front shocks work well in the front of a 2-3" XJ lift (just press the sleeve out of the shock's bottom mount and install either a BPE or bar pin in the sleeve's place).
As far as the rear is concerned - YJ rear shocks are shorter than the factory XJ shocks. For mine (3" lift), I used the rear shocks listed for an '85 Isuzu Trooper II. The shocks will require a slight modification for the upper shock mount - use either a BPE or reuse the bar pin from your old shocks.
ZJ rear shocks will also work in the rear (w/ the same mods as the Trooper II shocks), but it is my understanding that they aren't quite as long as the '85 Trooper II shocks so you won't get quite as much droop out of these.
Hope this helps!