[mustardjohn]

May want to look into lowering the car. That will make it handle a little better and want slow you down. You can get it down about an 1.5 inch. The '03 sort of has ground effects on it already and lowering the car brings them out. Not sure what you would pay for ground effects but lowering an new wheels is an option.

Here is pic of an '01

http://www.fast-autos.net/ford/fordbullitt.html

another lowered Mustang

http://www.cardomain.com/id/celsyus