On having harnesses in your car:
1. The Low Volume Standards allow for full-harness belts, but only in single-row seat scratch-built cars like custom-built sports cars, kit cars, and hot rods.
2. The only way to have a full-harness belt in a production road car is with a Motorsport NZ Authority Card. This doesn't provide for import drag cars though.
Edit: which means I can have them in my car no worries