AutechKouki

If you want a gear ratio that's right for the cd009 with a s13 subframe you have plenty of vlsd options without having to spend too much or fabricate anything.

1. There's the 96 and older Q45 rear differential with a 3.53 gear ratio you could run with 6 bolt 350z axles and keep factory s-chassis hubs.
2. 97-01 Q45 diff with a 3.69 gear ratio and run J30 axles and keep s-chassis hubs.
3. 92-94 J30 rear differential 3.96 rear gear ratio with matching J30 5 bolt axles, of which is a direct bolt in and has the speed sensor that'll work out best with your cd009.

Keep in mind that the half-shafts from the Q45 are interchangeable between the first and second generation, meaning if you wanted to run 350z axles on a 97-01 diff you would have to source the older half-shafts and they would drop right in. They have a higher spline count so this is only true for Q45 diffs from my experience.