the rep also told me that from start to finish a 2013 gt500 is built in 4 days from start to finish, from the chassis being built, then being pulled off the line to get the Shelby treatment, to painting, to quality control..... that all happens in 4 days. I don't know if that helps you at all but that was way less then I expected.
It was my understanding that the Shelby's were built on the same assembly line as the rest of the mustangs, no mention of them being pulled off the regular line and being finished on a niche line.
I can't believe that there is not one Auto Alliance plant worker on any of the forums, he or she would be a great source of information and would be able to clear up some of the myths surrounding the assembly process.