the law states, if the instrument clocks fail and new ones are fitted, the new clocks can be adjusted to the old value, as for engine changes, the mileage is what the vehicle has covered not just the engine, to keeps things all above board and within the law the mileage must stay the same.
.......but it can be done, and as long as u are honest and explained u had the clocks corrected to the engine, u should be ok.
i have the same thing with my 8v mk3, i converted it to 16v abf last summer, the engine came from a 91k m plate, and my 8v had 141k on it, so my clocks are saying around 143k now, but i have no proof that the engine done 91k!.
The correction law was only changed because of all cars have lcd dashs now, and getting on a bit now and failing, not always the mileage lcd failing but like on skoda's and some audis other parts like fuel gauges failing, so have to change the whole clocks.
When i go to a customer for a mileage correction, i do like to see the old clocks plugged in, as i wouldnt like to buy a car with dodgy mileage like anybody else wouldnt.
