What are the differences,if any,between a 2004 and 2005?

 

Too much to list. While the C6 is based on the C5 it really is an much changed car: about half of everything is really new. Go look at both back to back. The motor is basically the same with the base C6 having just a tad less performance than the C5 ZO6 but more than the standard C5.