The standard callibration of the speedo may include some 'flatter'! In the era, manufacturers routinely made their speeds read high.On the bottom of the speedo face is R136J. I assumed this was that it was used on any Fuego as their R No. is 136X., however most speedos have the rpm that sets them for either 60 MPH or 100 KPH. written on the bottom of the face. As my drill is 1600 rpm then 100 kph could be about 1360. My assumption is that the J could vary depending on each individual speedo. Now 1600 rpm is 17% more than 1360. I have pruned a small amount off the needle weight and am getting closer. I'll keep trying. The "0" box allows for the needle to be adjusted any where in the box and therefore still be counted as zero.