A Code GT's?

What gives? I thought that the only GT's are the K codes, but when I was looking on line for a playmate for my Stang this morning I came across about 6 "A Code GT" cars. Please correct me if I'm wrong, I know that Ford did some wacky stuff back in the day.
 
GT could be on A-code or K-code; as long as it was a 4bbl 289.
Most of the GT's I've seen for sale have been A-codes, or else they would all be worth A LOT more if they were all K-codes.

At the same time, you could get a K-code without the GT stuff.

One thing I'm not clear on is that I know sometimes the GT stuff was a dealer installed option. So are they any C-codes running around with dealer installed GT packages? Or were there restrictions from Ford telling dealers to only put the GT stuff on A & K-code cars? Also, would dealer installed GT package cars have the rocker mouldings and the GT stripes? What about the badging differences?:shrug:
 
A codes were available with the GT option but be careful, lots of people try to pass off converted A codes as factory original GTs. If you know what to look for you can tell if the conversion was not done correctly, but it's really hard to verify if it was expertly done unless you have documentation. But, if the price is right, the car is sound and originality is not so much of a concern I'd go for it.