There is no law in this country about changing speedo heads.
There are companies who will 'adjust' mileage readings but I think you would be better off just keeping a note of the mileage the speedo was changed at and keeping the old speedo so when you sell the car you can just be honest and tell any potential buyer that its been changed because it was faulty and show the old speedo to prove it..
A lot of the early facelift 156;s had speedo changes as a recall after over a year so many of them are not showing the correct mileage but it should be noted on the service history.
When I bought my old 156 it was advertised as having 38k, after looking through the service book there was a note about a speedo change at 32k miles that the sales man hadnt seen, his face was a picture when I showed him
Last edited by JON156VELOCE; 21-06-12 at 15:26.