what i meant was can you just add a 4wd front housing and an input shaft and shifter and make it a 4wd case?
Yes, you can.
You will need the shifter part of the tcase (that bolts in place of that plate on the front side of the 2wd case, the shifter, shift rails, couplers for the front output, a front output shaft, and you can add the 4wd indicator switch to the shifter housing.
As mentioned though, it may be cheaper to just find a 4wd case or find a 4wd with a broken case and swap the parts over to the good 2wd case.