From what I am lead to believe, the GT's are only just going into production or just coming off the production line. There are none around as far as I know.
I'm also pretty sure that the B200GT is also the standard King Air now. The 'old' B200 with the -42's is no longer in production. So you order a B200, you're gonna get a B200GT,
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Happy to be corrected of course.
morno