I'm not sure if the GT has the same placement as my 270 (it mounts above the full length side molding), but here are some pics, passenger side:
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Measurement from rear edge of fender:
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Measurement down from main character line (trick of the camera, but the end of the tape is exactly on the tip of the body line):
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Sorry for the quality, but it's pretty cramped getting at the car in storage right now, plus it's kind of dark in there at midnight... :)