If everything else is Campy 9, but the rear wheel takes Shimano cassettes and is currently equipped with one, and you want to use Campy, then I'd advise just getting a Campy-compatible rear wheel and a Campy cassette, then sell off the Shimano-compatible wheel. There does exist a "conversion" cassette that uses Shimano-style splines but Campy 9sp spacing: http://aebike.com/product/wheels-man...w4583-qc30.htm But you back yourself into a corner... one manufacturer, one available ratio, and quite expensive.