Attached below are photos of a Carrera Tail and a Turbo Tail from similar years. As you can see the profile of the base is much different. You could put a Turbo base on a non-turbo car, and I've seen it done quite a bit, but you can't put a Carrera base on a turbo car, as hole in the turbo decklid is much bigger as noted above. Technically, the two piece support is for the Carrera Tail, which would have been supplied with Option M473, and the one piece support is for the Turbo Tail. But also as noted, I can see any reason that either wouldn't work with either.
