First not sure where your 2111 convertibles came from originally. As far as we currently know Ford no longer has production records that you are looking for (destroyed
I'm sure someone will post that Kevin Marti does but unfortunately he doesn't
Sorry
As you have likely already figures out a combination, as you described, was very unpopular (as were bench seat s through all years of production). I would assume that you have already confirm for yourself that you do have a factory GT and an original door tag. Though not everyone is, we often see these odd combinations on cars that previous owners assemble in order to have a car that stands out. Please understand that I am not suggesting that these are the fact in your case. As only one of us has seen the car
Good luck with the car
Jeff Speegle
MCA Shelby Gold Card
http://www.geocities.com/MotorCity/6473
Mustang & Shelby research, documentation
http://albums.photopoint.com/j/View?u=1609818&a=12284202&p=44925357&Sequence=7&res=high.jpg