Hello, And welcome to the site.Your car is beautiful.That being said Ford never officially built a Summer time edition in G.T. Form,That I know if? I remember the Feature cars quite well and was very active in the late model/Ford scene when those cars were new.I've seen your color scheme interior before. Since you have the original window sticker,You're holding a nice piece of info,I'm not naming any names,but in the 80's and 90's there were alot of "Special editions" Done by individual dealers throughout the tristate area.So I would then possibly contact the dealer and see what they say.You'd be surprised,they may still have the original data on the car.You bought the car from the original owner,Did he order the car?Did he buy it off the lot,etc.?