There is a museum (in Okaya city of Nagano Prefecture) where you can see Nissan's major skyline cars.
I don't know if you can see there a Nissan GT-R car or not, but this museum is a must-visit place for Nissan car fans. The museum is called "Prince and Skyline Museum":
Prince and Skyline Museumhttp://www.prince-skyline.com/
admission fee: 1,000 yen
open hours: 9:30-16:30
open dates: April 14 - November 18, 2012 (every winter, this museum is closed due to snowfall)
closed every Tuesday
free parking lot is available
address: Torii-Daira Yamabiko Park, Uchiyama 4769-14, Okaya city, Nagano
This park is located about 1,000 meters south-southwest of the Okaya interchange of Nagano Motor-expressway, and 2,000 meters north-west of JR Okaya Station
Take a look at several images listed around the middle of this page:
These images show what you can see there.
There is also another Nissan car museum. This museum is called Nissan Engine Museum and located in a Nissan factory (Yokohama Works) of Yokohama city. You can see there Nissan's 28 historical engines.
What you can see there:http://blog.goo.ne.jp/a_kanatr/e/b59f3088d4bb74d16dbfef9bd67f5477
Nissan Engine Museum
address: Takara-machi 2, Kanagawa-ku, Yokohama
This engine museum is situated in the A1 area (shown below as a pink rectangle) of Nissan's Yokohama Works:http://www.nissan.co.jp/INFO/FACTORY/YOKOHAMA/map_museum.html
The Yokohama Works is located about 1,000 meters south-east of Keikyu Shin-Koyasu Station or JR Shin-koyasu Station. It takes about 17 minutes by walk from either of these stations.
The official site of this museum (written in Japanese): http://www.nissan.co.jp/INFO/FACTORY/YOKOHAMA/museum.html
admission fee: 0 yen (free)
open hours: 10:00 - 16:00
closed on every Sunday, summer holidays, and New Year's holidays