If you want to go to all the trouble, and I think there might be merrit with such a low milage car as yours, I would go to the AA (or whatever automobile assosiation in your country) to get the milage with the old odometer verified and a certificate issued, go home and replace the odometer, and go back within a few days and get them to seal the "new" odometer and issue another cirtificate stating what was done. Can't guarentee they will actually do this, but might be worth a try. In South Africa the police will also do it for you, if I remember correctly, but it has been a while since I've been there. Here in New Zealand there is a huge range of vehicle certifiers, due to the relative ease of importing a vehicle yourself, so here it is very easy to get the verification done.

I like the idea of setting the "new" one to zero.

A drill will take a long time to "clock" the odometer. Much easier to break the seal, open it, and lift the springey things that hold the wheels in place. Then just get it sealed again by the AA. This includes sealing the mounting screws between the odometer and the body. But breaking the seal on the odometer might raise the suspicion (later on) that the gear ration was changed. But I would not worry that far into the future about something that might never happen.

Have fun...

'71 144 113 000km
'88 240 94 000 mi