Those are good mileages (the ranges that you have mostly noticed to be between 150-200k). Those ranges are probably the norm for most 7.3's between the ages of 98-02. My 01' SD CC had just turned 200K when I bought it.
I'm not a pro at this but I've learned a decent bit since I've started here on the board, so here goes:
First thing above all, if it's an automatic, try to get as honest a service background on the tranny as you can, if you can. The 4R100 tranny has left a sour taste in many-a-mouth of the modern powerstrokers. It has failed many times, to many members. You'll read a bunch here on the board about ways to help improve the life. Such things include adding a second trans cooler. I did this to mine and have seen temps drop as much as 30-40 degrees. The stock cooler doesn't cool well especially when you leave the front license plate holder on during the summer months. Basically keep a good cool running transmission, with good clean fluid. The tranny is all but GUARANTEED
to last you longer if you run it cool, and keep it serviced properly. Nuff said about the tranny for now.
Second, check it for oil leaks. I haven't read that much about the HPOP, but it has a couple of seals that like to leak some. The Ford dealer would like to replace this item for you for a whopping price (no surprise). A few of the guys on here can help walk you through a simple fix with a little time and about $8.00 bucks worth of seals.
Lets see here. Third, if possible have the batteries tested. If one is bad, or really weak, REPLACE THEM BOTH
. Don't ask why, just replace them
It'll save any potential alternator and electrical problems. You want the batteries to be as new and fresh as possible, BOTH OF THEM
, when you replace either/or. This might be a bartering angle you could use if you can check them before you buy. They're about $100.00 each new.
Also, regarding fuel, if you do buy it, plan on using some type of additive, because the ULSD stuff that is being sold now, lacks the necessary lubrication for older diesel engines. You can get by with adding something every other fill-up, but it would be preferable to add something each fill-up. Certain recommended additives are StanaDyne, Diesel Kleen by Power Service, OR, some people here like a good ashless 2 stroke oil - No more than about 4-6 ounces with each full tank.
Well, I'm running out of ideas here, sorry for the long wind, but I've nothing better to do until about right now, Plus it'll give you something to read if your bored
Anyway, the engines (7.3's) are total workhorses and properly maintenenced will last you albeit a toe tag
Good Luck on your buy. Should be fairly easy and not too much to look for. They are great trucks, really. And you can get a feel for it by looking closely overall, for starters
Oh last thing, check the suspension. I just replaced 4 worn out shocks, and my local trusted independent shop guy also sold me two right side ball joints (upper and lower).
Again, Good Luck on your buy, and if you find a truck, take the time and post it up here and let us help ya on that particular one. We will the best we can.