The British also used Packard-built Merlins during the last three years of the war in their Spitfire, Mosquito, and Lancaster aircraft. I doubt there was much interchangeability between the Packard and Rolls-Royce produced engines. Packard created all new blueprints tailored to U.S. manufacturing standards. The initial Packard modification on the Merlins were done by changing the main bearings from a copper lead alloy to a silver lead combination and featured indium plating. Indium plating prevented corrosion that was possible with lubricating oils used at that time. The bearing coating also improved break-in and load carrying ability of the surface. British engineering staff assigned to Packard were astonished at the suggestion but after tear down inspections on rigidly tested engines they were convinced the new design offered a decided improvement.