Ask over at 3.8mustang.com. I'm willing to bet that you can find someone who'll give it to you for free. Upgrading to duals is a popular mod for that crowd. When I had my 3.8 and upgraded to GT duals, I ended up just having the shop throw out the stock setup.
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