You are going to need to do several things. Here are some of them that come to my mind: First, you will need the 4x4 adapter housing for the back of the transmission (replacing the 2x4 tailshaft). Next, you will need a compatible transfer case (I believe Ford used a Borg Warner case, but I do not recall the specific models). Additionally, a front drive shaft and front 4x4 axle will be required. Your rear drive shaft will have to be shortened. Next, You will have to have some means to control the 4x4 function, either by a lever or by a switch. Also, if you have the E4OD transmission, the PCM for the 4x4 version have codes for the 4WD system. If you do not install a 4WD PCM, then you might have problems with your configuration. Lastly, there are lights on the instrument cluster which illuminate when the driver activates the 4WD system. Although perhaps not absolutely necessary, these can be helpful. These are just a few of the modifications which I can think of. There might be more.
Both of those units are four speed overdrives with locking torque converter. They both have the same shift pattern: PRN(D)21 with an overdrive cancel switch on the shift lever. The C6 three speed (which I do not believe your truck would have, although I could be wrong) has the pattern: PRND21 with no overdrive switch. The C6 has 17 pan bolts.