Those are for the 280zx which have a completely different suspension design than the 240/260/280z.
all S30s require coilovers to be welded on.
i personally just used integra coilovers (welded the bottom bracket to the strut tube), but there are other options such as the ArizonaZcar coilovers
coil over suspension as well as serialnine's conversion tubes which allow you to use stance coilovers.
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