Have you looked into theTechno Toy Tuning setup?
It'll allow you to use the diff, axles, hubs, calipers and e-brake from the donor Nissan car (240SXs, Skylines, Q45, Z32 NA, or Z32TT).
Since you're thinking of going the R230 route, the Z32TT hubs are stronger (31 spline) than the 280Z stub axles (only 27 spline). You can source them at the junkyard for pretty cheap, and the Q45 shares the same hub as the Z32TT, making it even easier to get replacements. No need to get stronger stub axles or CV adapters like in the other kits.
The rear CV axles are also the same between the Q45 and Z32TT where only the length of the center axles may differ slightly...this doesn't matter as TTT has replacement centers in the correct length for the Zs. You send them your pair of axles and they take them apart and install the new centers.
Where are you located? I have an R230 and some other parts if you're interested.