If you change the diff you'll need to use a diff cover from a series I (non-vspec) GTR. Any aftermarket LSD won't fit the A-LSD backing plate.
If your spinning only one wheel, it might be time for an LSD oil change. If that doesn't fix your problem, might be worth having a look at the diff out of the car.
The A-LSD's aren't too good at holeshots but they're very helpful around corners at speed. It depends what your using the GTR for.