Bought a '00 5.9 2wd new. Got 15-16 in town and 22-24 hwy depending on how I drove it. Ran like a scalded cat.
Couple of years ago I bought another '00 5.9 4wd w/ a bad engine. Scored a recently rebuilt 5.9 for it. Drove it a short time and had to do the solenoid/sensor deal. Drove it a little longer and trans went completely out. Did a 5 spd. swap instead of rebuilding the auto and absolutely love it. Mileage picked up in-town about 1 mpg BUT I need to do the plenum gasket as it's sucking oil. Maybe the mpg will pick up a little after that. Never have checked it on hwy. but it seems about the same as when it was an auto (15-16).
Unless you need/want awd or 4wd I would stick to 2wd for the better mileage. If I had known 4wd was that bad I sure would have.

If you want to travel a little craigslist around here has a good selection of what looks like clean ones (especially bad 4.7s).


Tim