I've got 178K on my '03 and it's still running strong. Original everything still in/on the engine (except fluids of course). The 7.3L is an amazingly reliable powerplant (the engine was pulled from the medium duty commercial market and dropped under the hood).

Besides the OASIS, have the owner get the maintenance records from the dealership that worked on it (if he took it to one). Dealerships also keep their own database for each VIN they work on. I am the second owner. Original owner was a horse rancher and had the truck serviced at the same dealership he bought it from and the local maintenance records from the dealership were very helpful.

If you can find a mechanic that knows the Powerstrokes, it would be worth $100 for an inspection to see what's up with the truck. I can tell you with those miles that you are looking at ball joints if they haven't been done recently ($250 for parts + labor cost if you don't do it yourself...maybe 5-6 hours worth??).

The only other things I can think of for an '01 is that sometime that year the front axle was upgraded from a Dana 50 to a Dana 60 and there was a mechanical diode issue with the transmission. You should ask the owner what transmission work/replacement has been done over the years and if he knows if it has the mechanical diode. The diode can fail and the tranny is done, but it's an easy fix (I don't know how cheap though) if you take care of it before it fails. With those miles, chances are that it's on it's second tranny (at least) and the problem may not be an issue any more...

Hope this helps. Good luck with the rig! Miles aren't as big an issue with these trucks as much as their care. Age does play into wear, though, especially up front with suspension and steering. 4000+ lbs riding up front would be tough on anything! As long as you know what you're getting into, you won't be disappointed.

Welcome to the club!