28-29 coupe doors are the same as Tudors. 30-31 Coupe doors only fit on 30-31 coupesor sport coupes. They are about 1-1/2" narrower and about 1" shorter than 30-31 truck or tudor doors
Dave's right, with slight variation. If you can get 26-27 T doors for your 28-29 closed cab pickup or AA, you'll be fine. If you have a 28-29 AA and need an express bed, a slightly modified 26-27 TT will work with some modifications but won't have the wheel indent that a true AA express bed will. If you're going for judging points, it's important. If not, who cares?
An easy way to tell a 30-31 coupe door from a tudor or truck door, The hinge will be about 3 inches from the top of the door while the tudor/truck door will be 4 inches. Check it out next time you're at a show.