XUD running rough and grey smoke. possible Hydro

[Dave]

If it runs, revs, drives, sounds fine, with no smoke, no coolant pressurise or oil loss , or moisture out the back no funny knocks then its fine. If its buggered your engine then it wouldn't be time dependant like what happens after 60 miles, that must be something else. It could potentially have nailed a rod and bent it slightly, but in my experience this causes no noticeable effects, the best thing to do if you're really concerned about that is whip the sump off and have a look at them, it will be clear if any of them are bent. Also depends how they were driving it through the ford, if they are at 4k it wouldn't have done it any favours... but if they were just ticking over through it, it would just stop the motor, and require a flush.