I've had alot of experience with the 4.7L's and they have been bulletproof for me for many many many miles. With that said, I bought all of them new and maintained them properly from the start. Without maintenance they seem to fall apart quickly.

I'd take a 4.7L stock for stock over a 318 anyday if I had really good documentation of its maintenance history. Without that I'd probably go 318 unless the 4.7L was very low miles.

-Jon