Sometimes less is more. If you want to clean up the front end of your '99-'04 Mustang try this grill delete kit from Classic Design Concepts. Another must have modification for your Mustang!
More details available here: http://www.autohow.tv/node/16
In 2003 and 2004 Ford offered a special edition Mustang: the Mach 1. The grill delete was just one of many changes including a shaker hood, more powerful engine, different gearing, etc. You can now buy a kit to convert your Mustang GT or V6 grille to look like the Mach 1! As you saw in the video it's a pretty simple install.