I think there is a 300lb or so difference between the stock Camaro and Mustang. But as I have heard, you cannot put enough bracing on the Mustang. There is quite a bit of weight added to the Mustang in bracketry and bracing to fix their sins. So I do not think their is as much weight advantage as initially discussed. But I will repeat, I believe the Camaro has at least a .3 second advantage over the Mustang.
Time will tell once everything is posted