I looked at this option and passed. You just do not know what you are getting.
I used to work for a DOT and w had trucks that sold with only 10k-50k on them. The problem was they were from Airports or jails or some other facility where they didn't move much but were left idlling for 8 plus hours a day.
I am just finishing a rebuild and had a long-block done for me by the cruiserparts.net guys and they did a good job. Doing it all my self and replacing every hose, fuel injctor, h20 pump, fan clutch, oil pump and more that I' can't think of right now and I'm into about $4500 or so (I did some other things as well so that number may be high).
Good Luck
BILL