Note: This game is also titled The Rolling Western.
Successfully complete Stage 3: Day 1 to get the Ancient Buckle. This item enables Arma-mode, which allows Dillon to become invincible and do triple damage to enemies.
Successfully complete the game, and earn all 50 Stars to unlock Sal's Hut map location. You can see 3D models of all the Grocks at this location.
Successfully complete the game, and have at least $100,000 in savings to unlock The Old Mission map location. You can fight a hidden Boss at this location.