Okay I have "witnessed" taking apart an odemeter and trying to put it back together to have a corrected reading. Everything will look right when reassembled until you go to move the numbers. Then they seperate a hair and show these black lines between the numbers. That's the sign that the odom has been tampered with.

If you're deadset on fixing this, go to a junk yard and buy a cheap speedo and practice taking it apart a few times. You'll need the practice. Otherwise contact the DMV and get a variance for your title. They'll send you a card to verify non-actual mileage.