The 3.8 doesn't need a cross over (x, h pipe) because it has an even firing order (unlike the 4.6), hence doesn't have the change in pressure to worry about. It may sound a little raspier than it would with a crossover, but IMO not enough of a difference to warrant a change. Stick with what you have, and if you don't like the sound change mufflers.
2002 Mineral grey GT 5 speed. Flowmaster 40's catback, Mach 1 grille delete, timing advance, push button starter, Bullitt pedals, FR500 steering wheel, K&N FIPK, Self ported upper intake w/ spacer, Pioneer Avic D3, MGW shifter, MM FL subframe connectors, Mach 1 springs, Bilstein HD struts/springs