Isuzu has made some great tough motors! They make the Duramax diesel for GM. The 3.5L pulls strong and most of them seem to last a while... there are those select few that give up the ghost a little early though. Some people have experienced gasket leaks at the manifold, I believe; and the oil disappearing is a strange occurance. Otherwise, my own personal experience with my 3.5L has been great. I am about to hit 58,000 miles on my '99 without issue since I bought it a year and a half ago.
Sent from my "two hands on a keyboard"