One thing that's important to keep in mind regarding the factory, and probably the aftermarket signal light kits as well; they included replacement sockets for the front lamps. The front lamps were simply parking lights and have single element sockets. The kits came with direct replacement dual element (terminal) sockets so you could have both parking and signal lights in front.
Also, the kit likely mentions that you have to tap into the brake lights for the rear ones. On the Henry J, there is a junction under the dash you can simply unplug and plug the terminals on the signal light kit into it. No need to cut or splice, use the factory junction/plug.