For your information i do know a few skyline specs.....
This is what i know
The GT-R came with the LCD screen in the centre of the dashboard
The GT-R V-Spec added two extra features to the display, the first being a measurement of lateral g-forces, and the second being a lap timer.
The GT-R M-spec Nür and GT-R V-spec II Nür had softer suspension, and a leather interior.
The R34 GT-R N1 did not have ABS, Air-Con, audio equipment, rear wiper, or carpet in the boot. Of course the lovely N1 engine was added
The V-Spec II GT-R model has increased stiffness in the suspension and a lovely carbon bonnet!
The Nismo R34 Z-Tune was bored out, with a new crankshaft for a longer stroke and had a 2.8l engine, producing around 600bhp! oh and a believe it had a supercharger! Although
The Nismo R34 Z2 had all of the above but had simular body styling to that of the Nismo GT500, so engine bay vents on the bonnet and wheel arches. Also had bigger arches to take some bigger orgasmic wheels!!
Oh and both Z-Tunes are also completly hand made! so very pricey!