Mk. XVI - the exact same thing, but with the General Motors "Packard Merlin" replacing the Rolls-Royce.
Naughty, naughty, Danny. Nothing to do with General motors. From Wiki:
In 1942, the Packard Motor Car Company converted to 100% war production.[31] During World War II, Packard again built airplane engines, licensing the Merlin engine from Rolls-Royce as the V-1650,