Drivers Republic recently pitted a 911 GT2 vs an R35 GT-R. The 911 was supplied by Porsche, the GT-R came via customer though Japan. The story is here.
Chris Harris was the driver and he drove each car for three laps (one out lap, and two flying laps). Chris successfully competed in the VLN race that weekend so was race-fit and needed no acclimatisation with the circuit. On a slightly damp track, the GT2 goes 7:49. The GT-R goes 7:55. Videos over at the Drivers Republic site.