It's apparently been resolved, and the calendar is being printed as is:

http://www.bmcforums.com/showthread.php?t=42820

From that thread:

"My name is Whitney Drake and I work in Ford Communications.
We've been watching this discussion with interest and I'd like to
clarify what is essentially a misunderstanding.

Yesterday we spoke to both Cafe Press and the Black Mustang Club
and explained the situation (about the Black Mustang Club’s calendar) to everyone's satisfaction. Ford has no problem with Mustang or other car owners taking pictures of their vehicles for use in club materials like calendars. What we do have an issue with are individuals using Ford’s logo and other trademarks for products they intend to sell. Understandably, we have to take the protection of our brands and licensing very seriously.

Ford did not send the Black Mustang Club a “cease and desist” letter telling them that they could not use images of their own cars in their calendar. The decision not to allow the calendars to be printed was made by Cafe Press, because we had gotten in touch with them in the past about trademark infringements on products they sold."