First problems is, you don't seem to know a lot about what you're talking about.
Tachometer = RPM Gauge.
Speedometer = Vehicle Speed Gauge
SiR's use an electronic VSS to send a signal to the speedometer. There is information out there on wiring a 5th gen Civic's VSS to be used with the SiR cluster. The signal is the same. I think it's 3 or 4 wires. Power, Ground, Signal. Maybe one more.