I would not be surprised if the E3 part works since the cars are basically the same mechanically (for a given configuration). If anything, the E3 part might be slightly longer and that shouldn't cause you any problems. I think you should try to figure out if the cable end that goes to the speedo fits the CS speedo (I think it will). The other end will be OK. There seems to only have been one transmission drive setup.

Hi Bill

Would you know the differences between the cable for the E9 and the E3? I was hoping to use one I have salvaged from an E3 on my coupe, but they have diffrent part numbers. Strangely, the CD has the part number for the E3 speedo cable....068.