[BCreekDave]

The factory "backdrive" system originated from the column shift cars. Moving the column shift from park to drive rotated the column outside shell which in turn moved a linkage connected to transmission. When the car had a floor shifter, they just reversed the concept so the floor shifter would rotate the column shell. This then required the trans to be in reverse (since there is no "Park" on a manual transmission) in order to remove the ignition key. Most of this linkage system bit the dust as soon as headers were installed, thus making it one of the more valuable parts for restorations.