This the the tower brace that is part of the Track-Pak. I added it to my GT with 18" rims. I got rid of the car and I have the brace for sale $100 shipped.
I also changed my speakers out to Polk's. I even changed the subs to Kicker 2 ohm versions. You have to do some cutting and fitting, but they have much better sound then the stock subs
I test drove an '09 with 3.31s, all the 2010 Mustangs at my dealer had the 3.73 pkg. The 3.73s do pull better. I have the stick shift, FYI the 3.73 pkg only can be ordered with the stick. I'll let you know how the STB works out