The motor is exactly the same, different supercharger is mainly the only difference and it has drive by wire throttle control.

The block is same from both body styles. Transmissions are same aswell. Different internal parts and controls for 2003+ vehicles but all still suffer from the same weak points. 04+ tend to want a tranny cooler though.

You have alot of reading ahead of you that's for sure, not saying that to be harsh or anything but it's just the truth when you wish to get into modding.