The small cables you are referring to are, I believe, the ones that are included with most base plate kits. It is a fail safe that is meant to attach the base plates to the frame of the vehicle just in case something happens and the base plates break away from the truck.
You will still need longer safety cables such as # RM-649 that you have referenced to go from the base plates to the RV.
In addition to the tow bar, base plates, and safety cables, you will also need lighting on the truck and supplemental braking if you do not have them already.
For lighting you can use bulb and socket kit # RM-155. It bypasses the vehicle wiring so you will not have to cut and splice wiring but you will have to drill holes in the backs of the tail light housings to mount the bulbs. This is a great permanent solution if you will be towing the truck frequently.
If you will not be towing the truck that often I recommend a magnetic light kit # C-ATL20A. You will not have to cut into the vehicle wiring for this kit and it sets up quickly. Both of these light kits have a 4-Way flat connector.
Most states now require supplemental braking on the vehicle being flat towed. One of the easiest systems to set up and use is the Even Brake, # RM-9400, proportional system. It applies the trucks brakes in proportion to how much the RV is braking. This is the safest way to stop and it reduces wear and tear on both vehicles.
I have included a couple of helpful links on flat towing for you. Be sure to consult your truck owners manual for the proper flat towing procedures.