As stated, it can be done. We have a couple of people in the Mass Mudder Truck Club that have made the conversion with 2.9 engines and it has worked well. All the parts fit from a 4x4.
The only problem that did arise is that the frame is not the exact same thing. The front cross member is larger on the 4x4, does seem funny that they aren't the same but it must be the extra height that is needed for the front diff and the added strength required for the 4 wheel drive.
After a while the frames toward the front started to weaken and crack, OK so we fixed it but it happened two or three times.
So, if you get my point, the parts fit with a little extra lift but the frame is not up to the task. Although if this rig has a diesel then it may have a frame that is a little heavier, I do not know.
If you do the conversion watch the frame just behind the front wheels, that’s where the cracks started.
Oh ya, the header needed to be altered to fit.
GOOD LUCK!