So has this been done?
The S15 is a 6 speed box and mates to a dual mass flywheel.
Nissan silvia S15 6 speed gearbox conversion kit for s14 Complete kit. Drift | eBay
The S15 is a 6 speed box and mates to a dual mass flywheel.
Nissan silvia S15 6 speed gearbox conversion kit for s14 Complete kit. Drift | eBay