I just noticed that there is a second set of gauge lights between pins A25 and A24. Pins A25 and B9 got to 'fuse' and as such would normally be connected to +12 volts. Pins A24 and B10 go to the dash light brightness controller. If your LEDs are rated for full 12v, you should be able to connect pins A25 and B9 to the test battery +12v and pins A24 and B10 to the negative terminal (ground) of the battery. This will test the gauge lights only. If you have converted other lights in the cluster to LEDs, then you will have to figure out which pins are connected to those lights.
Just a heads up. In older simpler systems brightness control would be via a simple rheostat. In such a system, the lights are connected to ground through the rheostat. However, nothing is simple on an NSX. I had a quick look at the brightness controller wiring on the NSX and it is not a simple rheostat, so I am not sure exactly how it works. If it uses a pass transistor type regulating device, it may not work very well, or at all with LEDs. Then again, it might work just fine. Just don't be surprised that if you test the lights on the bench with a battery, it works; but, doesn't work in the car, or that the brightness control does not work very well. It will be interesting to hear how this works out.