Two excellent Mustang sources for parts and instal help....
Mustang Parts Specialties - ask for Greg
www.mpsautosalvage.com
They have TONS of late model Mustang stuff from 85-2005. I was just down there last week and they have a 2003-04 Cobra complete, runs great - parting out. It may be on their site under "parting out" They sell the whole front suspension, engine, 6-speed, everything for the conversion. Check it out. They are located in Winder, GA just above Atlanta. Greg is very knowledgable and has helped me out on my Mustangs a few times.
MV Performance - They do tons of conversions. Mustang performance shop and they do a lot of mod motor swaps. If you get stuck or are looking for help they can help you out. They're just down the road from MPS.
www.mvperformance.com
Hope this helps,
John