Forces from the cable is the only thing to damage a speedometer. The cable should come to it as straight as possible. The stop collar should be able to hug right up to the back of the input without applying pressure. Did you clean the old hard crud out of that square port?
The white plastic sleeve/clip on your sheathe is improvement over the collector nut that 67 and earlier had. Twice as long would have been better for the 50-year instrument life. The bell ringing noise was a rotating part hitting another part. There wouldn't be enough movement in the bushings for that to happen in a new speedometer. Good luck with it.