Unibodies flex and will crack at the weakest point. The rear panel as shown, the top of the quarters at the doors, and where the a pillar meets the cowl are the most common places. 4 speed cars are normally worse but it depends on how spirited the driver is. My GTX is an automatic and had cracks in all 3 places as well as where the rear springs attach. Yes it has had a spirited life. LOL.