Sam Mustafa's rules Grande Armee, now published by Scale Creep Miniatures, is available on Wargame Vault. You can now buy a PDF of these still popular rules for $25. USD.
The game has a variable turn/time scale. Ground scale is 1" = 100 yards, and basing is one stand = 1 brigade. Stands are 3 x 3" (batteries 1.5 x 3").
For a detailed breakdown of the game's very innovative mechanics drop by here.