First of all, kudos goes out to the Rixter for putting together such a precise and definitive list of all '89 GT's, plus other years as well.
Now I don't know if this has ever been mentioned before or not, but all '89 GT's also have option code 046 in addition to 639. I've owned enough '89 GT's to know this is indeed the case with all '89 GT's. For whatever reason, Porsche technically gave two definitive option codes to the '89 GT. I can find no website or otherwise to give me any different description of option code 046, so I'll just have to assume it also denotes "GT". And you'll only find option code 046 on '89 GT's. Never on any year before, never on any after.......
Porsche AG; those crazy guys!
Todd
