GM is preparing to introduce its most powerful convertible ever at this year's Lost Angeles Motor Show. We're talking about the 2013 Chevrolet Camaro ZL1 Convertible, a car that packs more power than a 2012 Aston Martin Volante, an SL63 AMG, a 2011 911 Turbo S or a 2011 Shelby GT500, which will go on [.]