My bad, I believe the LST F/R hub carriers and a-arms are not compatible with the LST2 and the XXL. The rest of the parts, aside from the extended chassis should be identical.
Alot of parts are interchangeable between the 3 LST variants but not all of them. Only differences between the LST2 and the XXL is the chassis on the XXL is longer which means the drive shafts are longer. The LST2 also comes with threaded body aluminum shocks. The XXL shocks are plastic. they are interchangeable however. The LST shock as far as I remember are not threaded body but are interchangeable. I'm not sure about LST1 diffs....I would look up the manual and compare them with the LSt2 diffs.