Your local auto parts store can usally order J bends and other angles with in a few hours if they dont have them in stock. But they commonly have at least one or two hanging around. 3" and 4" may not be on the shelf but usally just a wharehouse away.
Also the engine moves so be sure it can flex a little and not break. Also a main reason i dont weld the charge pipes and i dont have a tig on hand most of the time. But you want the charge side to flex. Front wheel drive even more so.