What similarities did the spitfire MK9 and the spitfire MK16 have in common?

The Mk16 was essentially a Mk9 with an American Packard 266 Merlin engine. At that period of the war (1943-44) the Rolls Royce Merlin 66 was required for Lancaster bombers, so Rolls Royce collaborated with Packard to set up manufacture of the Merlin in USA. These Packard built engines were fitted to the end run of Mk9 airframes (about 1,000 of them) and called Mk16.