Definitley swap the ZC into your Civic. You can even use your stock tranny. It's recommended to because the Si tranny has better gearing than the ZC tranny. As for the ECU...use the 88-89 Integra LS ecu for higher redline and fuel cutoff.(The Si ecu rev limiter is at 6800 and the ZC redlines at 7200) Just keep that in thought and you should be fine.
