I guess so, but the only thing you will beat it in is acceleration. It will be really hard to beat the mercedes in handling no matter what you do. If you keep all the creature comforts (just like the Brabus SL600) its going to be hard to beat it. But even if you dropped 50k into your mustang, it would not drive like the SL, the Brabus SL600 is just in a whole higher class.

Yes a mustang could beat one in a race, but it still would never come close to the quality and refinement.