I'm probably the last to know, just like I'm the last to know tire wear was flagged "on" instead of "off" as the default after Spec 2...lol.
But for what it's worth, there's a new GTR GT500 Stealth Model available free to North Americans only as I understand it. Here's a little bit about it and the code to download it.
gran-turismo.com
The fifth and final episode of GT Academy has aired on SPEED Network, and will be available for download from the PlayStation Store very soon. To celebrate this historic television show, we are proud to offer a free voucher code to add the custom Nissan GT-R GT500 Stealth Model vehicle to your Gran Turismo 5 garage, as seen in a special promotional spot during the final episode.
To download the Nissan GT-R GT500 Stealth Model vehicle, log into the PS3 with your PSN ID, and go to either the PlayStation Store and select "Redeem Codes" at the top right, or go to Account Management on the XMB and then select "Redeem Codes." Enter the voucher code shown below into proper fields and follow the on-screen instructions to download and install the car.
RD69-FJN9-5N6Q
The next time you boot Gran Turismo 5, follow the on-screen instructions as necessary to add the car to your garage, and enjoy racing this performance machine on your favorite tracks.
Offer good through January 30, 2012. Available while supplies last.