I know that my '67 didn't have one, but considering the car has a 556 HP 427 I elected to install one. They are bolted to the seat belt bolts, which means there are NO modifications to the vehicle. You'll need to purchase four 7/16 -20 jamb nuts and two 7/16 lock washers. Install two jamb nuts on the seat belt bolt threads that protrude underneath the vehicle, slide the driveshaft safety loop on the protruding threads. Place a lock washer on the threads of the seatbelt bolt, then the jamb nuts and tighten them.
The installation is just that simple.
NPD has a much better offering than the one Branda offers and they are about the same price.
-Dan