If you have another mode of transportation, I would not hesitate to perform a SAS/diesel swap on a truck. Big IFS are sh*t, to put it mildly. I would probably go w/ a simple leaf sprung suspension, as suggested by Trimble. I also would not put in a new Powerstroke, too much emissions garbage.
Trimble was correct in stating that you cannot go lower than a 4.88 reverse cut w/ the 8.8 IFS front axle. You also don't wanna mix ratio's...
I think it would be a better decision financially, and way more cool to SAS your Screw, and diesel swap it.
If you choose to retain IFS, and wanna hammer it offroad, expect to see a lot of snapped axle shafts, balljoints popped, and overall increased stress on the whole drivetrain from the strain of a huge IFS lift.