I would not depend on the speedometer at all for judging whether or not the odometer is calibrated. Doing so is relying on, either a 60 year old hair spring, or a potentially inaccurate hair spring in a re-manufactured unit.
The odometer is what matters. It is driven directly by the cable.
Carl

1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission