11.5 is what im running.. my heads a lil more tweaked than yours but I love my motor handles 5.0 mustangs just fine. But I will say this, if I were you I would go with a complete z6 bottom end. And get some pistons for that, for a better stroke to to bore ratio. I just got done with my na d series build, it has more than what you listed including some custom je pistons,that cost more than I care to mention lol. but ya go for either 11.5 or 11.9