I don't mean to sound bad here but you'd be better off purchasing a 4x4 vehicle due to the complexity, time and effort it would take to swap out dozens of parts. Still, if you must do the swap, shop around for a similar vehicle that is a 4x4. To verify axle fitment you can go to Yukon Gear & Axle
and find out what year front axle should be compatible. If you don't like to search you can contact them and I'm sure they'll help you out the best they can. I'd go with the NP transfer case. I've used them before and haven't had any issues. I can't speak much for the BW units, as I don't have much experience with those. To give you more ideas, search for Dr Evil Transmissions, and you'll see if a new trans is necessary to run the transfer case (I believe it is). Good luck!