Hi Tessa,

There are a few potential ways to do that. The easiest is to find a semi-transparent sticker to add to the car. It requires no specialist skills or tools and should be removable if needs be. These can be bought online for popular classics.

More difficult and permanent is to obtain a replacement speedometer face with the km/h markings on it.

The thing to be aware of with either of these, of course, is that the odometer will still be in miles.