Bahamut Replace Doom Gaze/DeathGaze?

With FF3 Sprite Editor (FF3SE), but I don't know it there will be enough space for Bahamuth if the sprite is bigger than Doom Gaze's one. You could always move the monster sprites somewhere else, where you have more free space, but that's almost advanced hacking (easy if you know what you're doing, but if you are new...).