I've used a Sierra as my main donor car, but the engine from a Mondeo. I have changed the engine number on the Sierra Log book to the new engine number. Do I say that the engine came out of the Sierra or fill in the forms with the Mondeo's reg number?
Any advice would be good.

what you get as a reg no ie q or not depends on points awarded ie the more of 1 car the better,they will know a zetec was never fitted to a seirra so play it straight you should have enough points to get an age related no

You will need to prove the age of the engine, if the examiner is switched on he will know that the engine is from a mondeo, you will probably need to run a cat.