Ixfxi, seems like you could lose a little more weight without being too extreme.
http://www.clublexus.com/forums/sc-4...worksheet.html
If you could get the SC into the 3200lbs range, I don't think thats too bad if you compare to contemporary sports cars or the heavyweights like the Supra. You probably have an auto. I have no idea what the 350z's cd009 might save you there.
As for rear diff options, theres always the Kaaz 2 way...