If it was a rolling start I reckon the mustang would have beat the GTR. Take the launch out the equation and it's not as quick as these type of races make it seem. My mates hybrid 996 turbos still pull on my other mates Svm 650r GTR from a rolling race.
The terminal speeds would certainly co platenfirm that (although not a lot in it considering the power difference). However, it would need to be well over 100 mph before it started to claw anything back at all and not everyone wants/can do that..
Those Mustang's are quick, but so so heavy.. I went up against a 500+bhp S/C'd one at Pod a few years back when my ED30 was only Stage 2. I had a sh*te start/crap run and remember thinking to myself "Game Over", but much to my amazement I nipped him on the line.. 
Agreed, if those Yank tanks aint made out of plastic they are made out of Pig Iron and damn heavy, I dont see the Boss getting anywhere near the GTR in a straight line and as for corners..................
A guy at my last golf club has a GTR (61 plate), offered me a drive, but never got time before I moved house, hopefully when I am back up there in October I will give him a call!, I followed out of the GC car park and up the main road and he gunned it from 40mph, I stood no chance even with 316hp, so quick standard, cannot imagine what they are like with 650-1000hp
