In addition to the Lufthansa operation for VW described above there was another operation in the 1980s by Alitalia and Lufthansa 747 freighters for Cadillac; cars were built under contract in Italy and shipped near-complete from Turin to Detroit. They were stacked at 45 degrees nose-down, there were 56 cars on each flight.
http://auto.howstuffworks.com/1987-1...c-allante4.htm