Let's start with what's been seen in person. A race team testing at the Circuit of the Americas caught the GT-R LM on track a few days ago, so Jalopnik schlepped out to the track the following day and took photos and video. There's a big ol' meaty front end where the twin-turbo Cosworth V6 lives, and that gives way to a trimmer back end. Mulsanne Corner, which has been following the car's development, figures the weight balance percentage is around 55- to 58-percent in the front through strategic placement of the KERS unit and radiators, putting it in the same division as proper mid-engined cars. A prop shaft runs from the KERS in front to the rear of the car.
It's speculated that the rear wheels are smaller than the front wheels because of that narrower rear end. In some of the Jalopnik photos the rear wheels do look smaller, which could explain the complicated half-shaft and drop-gear arrangement thought to be housed back there.
If all that is true this will already be the "radically different" car Nissan wanted to build. Yet there's more: Mulsanne Corner says the Nissan is targeting an ultra low drag setup, so there's a lot of talk about the car not having a rear wing, or only the hint of one, and Nissan plotting "mental" speed targets for the French track. Having the engine in front is what would offer more flexibility with the rear wing.
There's a good chance we'll know what it looks like on February 1, during the Super Bowl. Nissan will air a 60-second spot, and the advance tweet with the tagline "We're Back" and a helmet promises something racey. There are more pics over at Jalopnik along with a brief video of it running at speed.