I'm building a 29 closed cab and have one 27 T door and one 28/29 A door.Obviously they look alike but here are the differences that I've noticed.The A has an internal lock mechanism while the T screws on to the inner panel.The hinges are different and need to be changed from T to fit A the T are segmented type while the A are hung at top and bottom of each hinge like a sedan or coupe.The window valences are miles apart in looks and not really interchangeable.These doors have become very hard to find and popular with the Rat rod movement.Most that I've found are really bad and years ago would have been chucked out.Fortunately today,good door skins are available for these as well as inner bottoms.Snyder offers them as well as Howell sheet metal out of Texas.Glad to hear that they are now offering the whole doors as repros,might drive the price of originals down a bit on the Ebay.