The convertible is heavier, because it has extra bracing in the frame that weighs more. Also the engine has 150 horsepower, while the 1999-2004 Mustang has 190 horsepower. So with more weight and less power, it will definitely be slower. The automatic will slow it down even more.
i have a mustang 96 stick shift and they is no way im changing that for a v6 automatic unless the other car is better in many ways besides if you like to race stick shift has advantage and i love that you can control the rpms and that kick a automatic *** unless is been modify under the hood