From what I know, the GTt and GT coilovers should be the same. GTR's different. So if you've got a GT and can only find GTt coilovers, they should be fine. Even four door and two door, they should be the same if they're both GT/GTt. If you've got a GT4, either four door or two, you should get GTR coilovers.
Correct me if I'm wrong guys.
Edit: Don't listen to what I just said. It's wrong...