bmac:
If you want more info on H1s go to the following link.
http://www.amghummer.com/humdefault.htm
Everything you need to know about years to buy and look for can be found on this site as well as what to look for in the number 8 cylinder.
I bought my H1 about three years ago. It is a 97.5 with all the upgrades done and the motor replaced. I agree with Carey it should go over 200K miles.
The other mailing list has much more info on H1s, including a list of high mileage hummers.
http://www.humvee.net/hmh.html
Check out the two links and this should help answer some of your questions.