wiring the fan is relatively simple fused battery feed to the battery/ 30 terminal, wire to the fan goes on # 87 on the relais. ignition hot goes to either # 85 or 86 the ground for the relais you switch with some kind of temperature controller or switch most temp controllers use a probe you stick in the radiator fins near the upper radiator hose you can also find a temp switch that you stick in the cyl head near the thermostat housing.
I am pretty sure ISPRO makes some of these switches or use a fan clutch switch from a big rig. As far as the factory wiring goes you can use the location and the fuse, however most factory cooling fans get controled by the ecm so that part is a bit harder to do, still possible though if you find the correct ecm
