2010:
In Europe the tuned down the engine from 243 to 241 kW to meet emission standards.
2012:
added Oil cooler
2013 FL:
added sound deadening
Allthough I think all the fancy pieces of paper from Nissan always stated 5.3s from 0-100km/h (62mph) for the manual and 5.6 for the Auto. 5.2 for the Nismo.
0-60 normally seems to be roughly 0.2 less.
But, several tests seem to have high 4s for the car in general and normally a faster time for the non-Nismo as the suspension is a bit softer, weight shifts easier to the accelerating wheels and therefore generates more traction.
Nevertheless I can guarantee the normal 370Z Sport with the AT is the fastest Z on public roads.
Otherwise driver-mod or bigger b* required.
EDIT: to sum up: I'd never buy an older car just because it
could be a friction of a second quicker.