Doing the SAS is far easier than swapping in the TTB Dana 35. If you think about it, it makes sense too. The 2WD Rangers are less likely to be beaten on and are quite plentiful. if you have your mind set as I do to make a 2WD a 4WD, there will be fair amount of work involved. First off, your gonna be swapping both the transmission and transfer case. Drive shafts will need to be swapped also. As for the SAS, your imagination is your only limit. There's a Dana 30 (some will say it's a weak swap and to not do it) Then there is the Dana 44. You could go nuts and do a Dana 60 also.
First thing you gotta do is sit down and figure out what you want and are expecting of this truck. If your looking for a reliable DD that may run the fire line roads every so often.. and not run any bigger than a 32" tire, than the Dana 30 will most likely do you quite well (the Dana 30 is "considered" a light duty differential). If you plan on doing moderate wheeling, than a Dana 44 would be better suited to your needs.
Your next choice for a SAS will be what front suspension to use. Four link... radius arms... leafs??? It all depends on you are expecting of your truck.
Hope this helps... Keep us posted on what your gonna do!