Stuttgart (dpa) — When Porsche presented the 911 Carrera RS 2.7 at the Paris Motor Show in October 1972, the sporty coupe struck a chord. Dubbed “the ducktail” because of its spectacular rear spoiler, it quickly became a bestseller. The planned 500 units were sold in less than six weeks and by the end of the year, the second 500 series was also out of stock. When production ended just under a year later 1,580 units had been sold and a legend was born. “No other of the many model variants of the 911 is as famous as the 911 Carrera RS 2.7,” says Constantin Bergander, co-author of a book about th…