I needed a longer one for my 544 when I put in an OD transmission. I got it very reasonably priced from www.gcp.se. What I discovered at that time is that the 544/122 gauge clusters had either a 'large' or 'small' speedo connection. The earlier models had the smaller, and the later the larger. I --think-- the later model clusters can be identified by the indicator light (charging, oil, high beam, turn signal) style - a small inset 'lens' is the older style, the larger (about the diameter of a pencil eraser) lens that sits on the surface is the later. I'm not absolutely sure the speedo connections changed with the indicator style, just a guess. The only difference between the M40 and M41 is just a few inches more length on the M41 cable.