I have built a roadster with a skyline R200 diff and hubs, axles etc. They all fitted well, but they were very heavy.. diff is 45 kgs on its own... I have subsequently replaced them with a wrx rear diff (22kgs), legacy axles and bolt on hubs from a later model legacy... total weight saving over 30 kgs all up. The legacy hubs are a lighter version of the nissan ones. The axles and cv's are much lighter and also have a better design. The rear track is almost identical to the nissan...
Have a look at my build diary for details on
http://www.lotus7.co.nz
yamaha powered 7