1)
www.EBAY.comWhen somebody (us, Europeans) is looking for such a especific car like a Pantera, people will look in the US Ebay as this is the place with widest offer. (I did)
2) Same applies to all american cars (Ford,Chevy,Dodge....and all Muscle cars)Biggest offer is in the states.
3)In my case, if I see and advert in Europe with an American phone number or contact, I will think something is wrong...(which may not be the case)
There is also a UK magazine, Classic and Sports Cars that I have seen in every airport around Europe, and everybody within "the industry"(by that I mean, that owns, or looks for a classic car)knows!
If I can be of any more help...ask!