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That powerstroke will probably outlast the truck so you'll have a hard time running it into the ground unless you ruin the truck at the same time. Then you won't be able to do your cummins swap.. No other comments if you're just looking to ruin a good powerstroke except find one with a bad motor.
Why would you WANT to run it into the ground? If you mean run the hell out of it, these engines will take a hell of a lot of abuse and beg for more. I think your best bet, like Darin said, is to find one with an already dead engine. With that, I can tell you that I've been looking for a truck with a dead motor and a working five speed, and I haven't had any luck at all. It seems like the only time these engines die is when the whole rest of the truck dies with it, from what I've seen.