These wiring harnesses are designed for your specific make and model car. The Painless™ company does a lot of testing and engineering on each harness kit to insure it contains everything needed to match your car perfectly.
The old harness is completely stripped out of your car and the new one is installed by a Master Certified Mechanic who has done dozens of these wiring replacements on classic cars.
This is just an example of a wire harness kit. Yours will probably look different since they are all designed for a specific car, and will have different parts.