Check to see if there are any sheet metal shops in your area. The ribs could easily be formed with a bead rolling die.
A press brake jig would be better for forming the receiver, since heavier gauge steel might not work so well in one of the die-and-form jigs.
If you're going to make a die for the ribs... Since the press brake can form the bends individually, Folding the top rails first would give you a positive location point for positioning the receiver in the rib forming die. Once the ribs are pressed, form the bottom bends and you're golden.