I have this done, you can read about it in the thread Stealth-Z originally started here: http://forums.hybridz.org/showthread.php?t=119780
Fitting the gauges into the pods was pretty easy, I even have the rear cap on the speedo now just had to trim it to allow the circuit board to stick out. Wiring the gauges themselves was also pretty straightforward once figuring out what pins did what, especially if you skip adding the high beam, e-brake and turn signal indicators in the pods. I am still working on getting lighting right in the gauges, the stock bulbs won't really work due to the PC boards, so at first I added rice bulbs for needle illumination etc, but ended up doing a LED light ring in each gauge also, which has helped quite a bit but there are still a few "hot spots". One of these days I need to pull the gauges out and do a more documented how-to on the wiring and cutting the pods/gauges as well as take some pictures of the finished product during day and night. I also still need to finish calibrating the gauges from km/h to mph, right now its a bit off especially at higher speeds.
Nice score with the Nismo cluster by the way!