The Roadmaster Sterling Tow Bar part # RM-576 that you referenced does come as pictured with safety cables, crossbar assembly with quick-disconnects, and a 6-way to 7-way adapter included. view full answer...
I personally went out to the warehouse to check on Curt trailer hitch # C13193. It does include ALL of the hardware including the self-tapping bolts. All of the hardware listed in the instructions, linked for reference, is included. I am not sure where the installer got that information.
If you plan on doing some towing you might be interested in etrailer ball mount kit # 989900. It comes with 2 ball mounts; one with a 3/4 inch rise or 2 inch drop and one with a 2-3/4 inch rise or 4 inch... view full answer...