I thought the adjustable suspension was only for the performance package, but I just saw the 2013 GT500 window sticker on this forum with the Bilstein adjustable dampers listed as standard equipment. I certainly hope this is true!
2013 GT500 ordered: stealth gray vert with sonic blue stripes, heated seats and electronics package
2013 GT500 ordered: stealth gray vert with sonic blue stripes, heated seats and electronics package