s13 and s14 boxes (s14 qith s13 bellhousing) are 50mm longer than the mk2 S12 style box, with the shifter position 65mm further back.
Mk1 s12 gearbox is hsorter still though.
shows mk1 s12 silvia (rear), mk2 s12 middle, s13 (or s14 with s13 bellhousing) front