Nissan 240SX Performance Modification/Differential/How to weld your stock diff
Weld side gears to spider gears and/or to case.
Welding the gears should involve 8 small welds with plenty of redundancy and it is removable.
Welding side gears to case and removing spiders produces a simple spool but requires a good weld.
Welding everything will give the most redundancy and strength for extreme use.