The Bullitt sway bars are junk, the front bar is 28mm (GT=26.5mm) and the rear is the V6 bar (GT=23mm).
Just get the Mach1 kit and buy a 2003-2004 Cobra front sway bar which usually can be bought for $70 or less. As for the rear bar the GT and Mach1 use the same 23mm bar. If you want to...