SoCal,
Just for future reference. The 4X4 means 4 wheels, 4 driven. That would make a 2X4 2 wheels, 4 driven. The correct terminology is 4X2. That will save some face if you hit one of the anal boards where a huge flame war will start over it.
As for Fabtech, that is an interesting question that really should be posed to them. The 2WD and 4WD share similar components, but the spindle is different due to the fact that the 2WD doesn't have a drive axle going through the center of it. For that reason, there may be a difference in ball joints between the 2WD and 4WD. You could verify that with Fabtech. I don't know too many people using their lift so I can't really say one way or the other. I do know that both CalMini and AC are selling their kits to both 2WD and 4WD X's, which would indicate that they are one and the same. But if Fabtech builds a weaker upper control arm, they may only target 2WDs with it since they have concerns about whether it would hold up under off-road conditions. Purely hypothetical though and as I said, you would be better getting it from the horses mouth.