There is no official "Episode 40" of a crossover anime between Fairy Tail and One Piece . The two series only have one official crossover special: "One Piece x Fairy Tail: The Great Battle in the Sky!" (often referred to as Episode 390 in Fairy Tail or a special in One Piece). Descargar Series Retro Gratis Blog Better Review
If you are looking for a fan-made series (often found on sites like Dailymotion or older animation forums) or a specific fight breakdown, here is a of how a battle between these two universes would play out, focusing on the debate of Magic vs. Haki/Devil Fruits . Battle Analysis: Fairy Tail vs. One Piece The Ultimate Crossover Showdown Video Title Gracie Bon Oiled Ass Camstreamstv High Quality - Video