Appearance-wise: slightly larger hood scoop, aluminum gas tank door, five-spoke wheels (a la the movie, which a lot of people now have), slightly different rocker panels/trim, aluminum shift knob, aluminum trim ring around around shifter, door sills with "Bullitt" on them.
Performance-wise: a larger twin-bore throttle body, aluminum intake manifold, and higher flow mufflers than those on the GT... spec'd at 265hp.