I've got a Draw Tite Part#24747 I purchased from hitchesforless on my 2010 Mustang GT. I originally purchased it for a 2008 GT California Special and had it on a 2009 GT/CS as well. I tow a Kendon Motorcycle trailer and one or two motorcycles ( under 2,000 lbs ) no problem. Yes they do fit the Shelby GT's and GT/CS dispite what you have read, just pinches the rear bumper a little bit.
The instructions tell you to drop the mufflers but you don't have to, just take one of the short carriage bolts to your local hardware store and get four 5 inch ones of the same diameter then you can just run the bolt through the frame instead of having to muck around with dropping mufflers and fishing the bolts into the frame. With a jack to hold the frame in place it shouldn't take you more than 20 minutes to install.
On my 08/09 GT/CS the standard 4 wire trailer light plug worked just fine, spliced right into the wires (read/white) in the trunk and ran the pig tail down out through the bottom left electrical rubber boot. On the 2010 Mustang GT (yellow/red wires ) I could not get the trailer lights to work with the sequential tail lights until I replaced the trailer's light bulbs with 1157 type LED bulbs.
-Chris