If you look carefully, the body steel for the front fenders is very different.
There is a crease that goes the entire length of the E46 body on the years including '03. The '04 starts the new bulbous trend that many (including me) are turned off by.
For example, the '04 led taillights. Can't be installed on earlier years due to changes in the body steel.
Jus' kills ya don it?