I am doing an engine replacement for a friend of mine and I need some questions answered and hopefully this is were I can get it. The vehicle is a 2004 envoy xuv with a 5.3L v8 vin p. My question is, what Is the difference between the 2003 and the 2004 engines? I have found some good priced engines but they are for an 03 and the guy is telling me that they have to be year specific. Everything that I have found is that they are almost the same exact vehicle from 2003-2004 with only minor changes. Anyone know what these changes were and why a 03 engine won't fit in the 04?