OK, going from 2wd to 4wd is really not practical at all. Espcially if you want to keep your IFS front end, you will not only need make the proper mounts for the front differential, you will also need new knuckles, hubs, transmission output, crossmembers, rear driveshaft, front CV shafts, ect. In the end it would just be cheaper to swap to a different truck, sorry.

However if you still want to pursue this converstion there is an option. You would need to swap to a solid front axle (SFA). The costs to do this right are HUGE, like 8k+ plus you will not be able to do anything cool like have auto track anymore, or push button 4wd. You will still need a transfercase, depending wether you go drivers or passanger side drop you can use either a divorsed GM or Ford transfercase. Also in a fullsize truck do NOT use an Atlas, they are not designed to handle the torque produced by a v8 and the weight of a fullsize. If you want to know more about a SFA go to some offroading sites and read up on it.

Thats all I've got

Conrad