the 5.2s and 5.9s are known to be good up to 200K miles, some even beyond.

I've had an 05 Durango 4.7 and had no problems at all in the 60K miles I put on it. bought it new and never had a problem. towed with it and it did fine too.

now I have an 04 Dakota with the 4.7, it's got 80K miles on it now, and haven't had any issues with it.

when it blows up, or gets valve train problems like everyone says they do, i'll post it up here, but I have a feeling the problems were only on the earlier 4.7s, (like the one in your ride now) where they had some PCV issues and the top ends would sludge up from water vapor. there was a fix that they did, I think in 03, which fixed the problem.

I've also heard that at some point, something inside the 4.7s changed, a tone ring on the crank or something, so you cannot take a later engine and put it into an earlier vehicle, without opening up the engine, removing the crank and changing the tone ring. I don't know the exact specifics, but I've heard of guys having that problem