To do a good job. All of them
As has been said all the wires go into the standard headlights.
But it is possible to get away with just the headlight loom. In fact you don't "have" to cut any, but hiding all that wiring without cutting them down is somewhat difficult if not impossible.
I guess you could go the other route and actually extend all the wires and hide the loom under the tank somewhere. Just leave a new tidy loom to the lights.
Either way it's going to take some fiddling.