So to preface this post, I am well aware that welding my stock diff would be a whole lot cheaper than what I am planning to do. With that said, I want to drive this car frequently in non performance scenarios and would like to avoid excessive wear on my rear tires so an LSD is a must for me.
From my research I have found two practical ways to adapt an LSD to my R180, one of which seems to be a lot easier than the other:1. Replace my stock open diff center with this unit from Quaife (
https://whiteheadperformance.com/product/quaife-qdf5l-atb-helical-lsd-limited-slip-differential-nissan-r180-diff-115mm-datsun-240z-280z-280zx-510/) and reuse my stock ring gear and pinion. My only concern is axle fit, I am unsure if this diff center from Quaife has 25 spline or 27 spline holes for the axles. Any input would be appreciated on this matter.
2. Replace stock open diff with a Subaru WRX STI front diff center ($75 junkyard special

) and have a machine shop fab up some hybrid axles using my stock axles and the splines off of the STI CV axles. Not sure about gearing, the STI ratio is 3.9 so it would be robbing me of some torque down low. Might see if I can't re-use my stock ring gear/ pinion set here too. Other challenge is going to be finding a shop that can confidently make me the axles that I need, will still probably be cheaper than the Quaife helical diff but would need to call for an estimate to confirm.
Please let me know your thoughts on these two plans/ if you spot any blatant errors in what I have come up with, I have read most of the other posts regarding this topic and am yet to find anybody really talking about what I have thought up here. Thanks