My thought would be get a Canadian speedo and have the miles set, speedo calibrated, it's just a gear, and both certified by a reputable analog speedo shop with a good rep.
That's what I did and now I have a mileage correct, 140 MPH speedometer.
Mine was done Dick's Speed'O'Tach in Phoenix in 2012 or '13. They're still around. Russ Kingdon. Hayden and McKellips, in Tempe, AZ