Are you looking to take the engine from another of the same MK, or are you wanting a different engine altogether?
I think you can take up to a 1.6 from the MK5 without too much issue but you need to bear in mind that the ECU probably needs transplanting too!
would the details be changed on the log book, so your insurance is still validated?
To be honest, its probably cheaper for you to sell the car, and buy a zetec or Zetec S with a bigger engine. By the time you do the transplant, code the injectors, pair the ECU, immobiliser etc, your probably looking at as much money as it would cost to just put the hand in the pocket and pay out the difference...
thats fair enough,
well in that case, as far as I know anything up to a 1.6 should be a straight swap in most instances, of course you would need the ECU also and probably the engine repairing.