Maybe (just maybe) that's because GTs are targeted at a more performance oriented crowd to begin with, so they beef it up a bit knowing the cars can and will be pushed harder.
FWIW, how many incidents of cylinder failure have there been in 2011-12 V6s?
Unless there are incidents of V6 driveshaft breakage under normal operating conditions that are anything more frequent than unfortunate isolated cases, I think Ford did its due diligence. As I said earlier, please direct me to a reliable and verifiable news story of Mustang driveshaft failures, and not an interwebz post.
Well,Ford using the 8.8 rear end instead of the 7.5 they have always used in the V6 leads me to believe they were thinking about drive train upgrade at some point.
Anyway I look at it the driveshaft in the 3.7 is inferior.