The official development of the mod for Medieval II: Total War concluded with version 6.4 . There is no official "6.5" release from the original team.
Because official development stopped at 6.4, the community created submods that act as the next version. Medieval 2 total war stainless steel 6.5 download
: Includes expanded character traits, ancillaries, and education/health systems for generals. The official development of the mod for Medieval