A good truck shop will have straight blanks that are threaded on both ends and they will have bending dies for most common shapes.
I have seen them heat the centers in a forge and bend and have seen cold bending with hydraulics.
If you do go to a truck shop try to watch them do the bolts and other spring fabrication. It's amazing how simple their processes are. They can take a flat piece of spring stock and punch, bend and/or forge it into custom shapes. Then heat treat it when they are done! I always loved to wait on the items I was there to get so I could watch them make them!