In that case, I'd say for sure look for a 7.3L; the 6.0L are not good for sitting for long periods like the diesels of old. Things like the vanes in the turbo can/will rust if the truck isn't driven enough. I know it sounds crazy, but it's one of those trade-offs for the horsepower.That's one of those moving targets. I'd say high mileage is 300k for most of them; though I've seen reports of several 7.3L & 6.0L with over 450k miles. Then I've seen folks that have neglected trucks that were a nightmare at 100k. I know of a '99 F350 that only got oil changes when it was at the dealership for some other issue (failed injector, toaster turbo, shelled clutch). The dispatcher that was a Chevy guy was constantly bashing that truck. I shut him up when I asked him if he treated his personal truck that way.