When did they last no release a shell on its own as well as the kits? I wouldn't be suprised to see a lightweight painted version available soon as well.
We dont have GT1 anymore in the UK only GT2 and stock (what you call GT3 i guess). In stock we have to use the wings that come with the shell in the kit, which is not always great as the newer shells like the SC430 now come with plastic wings not lexan. Not sure what a SC430 would look like with a racing wing on it. Might look a bit strange.