Barrett-Jackson auto auctions began humbly with a small charitable auto show in the 60s. Now, almost five decades later, the Scottsdale-based auction company hosts four highly anticipated shows across the country each year. The next big auction, to be held April 4 to 6, is likely to offer more than 400 rare and exotic cars at Barrett-Jackson’s 11th annual Palm Beach auction, located on the South Florida Fairgrounds. Highlights include a 1947 Bentley Mark VI with a Chevy V-8 engine and a 1970 Chevrolet Chevelle…