Some of the 03's had a head tick issue. That was eventually taken care of. The door lock on the driver side is black on a 03 and silver on the 04. The only major addition to the 2004 model was the introduction of Screaming Yellow (replacing Zinc), Competition Orange and the optional
Mystichrome paint scheme. The Mystichrome appearance package included a unique color-shifting exterior paint that was meant to be an improvement to the Mystic paint offered for the 1996 Mustang Cobra. The Mystichrome interior seating featured a unique color-shifting leather that mimicked the exterior paint. There may be other small differences that I can't recall at this time. I'm sure someone will chime in and fill in the blanks. Overall, its a great car!