TMK, there is no calibration of the speedo/odo possible with the stock ignition module. Some aftermarket modules allow this capability.
I'm sure that's right. We have a tv series over here on preparing and repairing Police vehicles (keeps a lot of people very busy!) and when they take in a new vehicle one of the first things they install is a new instrument pack, complete with 'calibrated' speedo.
Check for RECALLS with your nearest dealer. 04's had issues with starting. With the RECALL, dealer flashes updated data to the ignition modual to fix that problem AND updated the speedometer accuracy. Worked o my Wife's 1200 Custom.