Swapping 4wd onto a 2wd truck wouldn't be as simple as swapping your body onto a 4x4 frame, or just buying a 4wd out right.
As for swapping 4wd onto a 2wd. You'll need the front cross member, front axle hub to hub, 4x4 tranny, transfer case, front driveshaft.
If going with electric 4x4, shift module, radio bezel with 4wd switch, and shift motor.
Also, good welding skill. You will have to cut the 2wd cross member out of the truck and weld in the 4wd cossmember.
I think I covered it.