I agree that it would be too much trouble also. I don't think that you can you it without the rest of the SVT cluster, and I don't think the SVT cluster is plug and play compatible with the ZX3/ZX5/ZTS. The speedo is calibrated differently (it goes up to 170 instead of 130 or whatever ours does) and the oil pressure and oil temp have to go through the ECU prior to going to the gauges... etc etc.
Too much of a pain in the ass, if you ask me. Easier to do aftermarket gauges for these readings.