Just putting a 1.2 Transfer box from a Disco into my Defender 200tdi running on standard wheels and tyres. I have removed the 23 tooth red speedo drive to replace it with one to fit the thicker Defender speedo cable. So, should I replace it with another red one or the same one as the original box which I believe is a 20 tooth blue one but can;t get out to check? Also some suppliers list different version with extra letters such as FRC3313C8 - what does the C8 mean?