They will give you a form online to fill out. It asks basic questions like your PCM code, mods (CAI, throttle body, exhaust), tires size, rear gear ratio, auto or manual. It's pretty basic and very easy to go through. Assuming the V6 PCM is in the same location as the GT then it will be behind the kick panel in the passenger side footwell.
Sold - Black 2000 Mustang GT, gone but definitely not forgotten
- Silver 2007 Corvette
Current - DHG 2001 Bullitt