As Jeff pointed out, trying to determine whether a K code is a factory GT is difficult, because many of the features we look for on GTs (like dual exhaust and special handling package) will also be present on a non-GT K-code. Having said that, one important feature to look for on a 65 is the " half moon" cutout under the speedometer, which is difficult to fake. Of course, this cutout is also present on a pony interior car, but if you find on a non- pony 65, it is a good indicator of a factory GT.