[m22mike]

For 69 car's, those are shoulder harness belts, almost never used PIA. If you look at the complete front lower belt set, as installed from the factory, there will be two lower belts of equal length for both front seats . One is for a lap belt, and the other would clip to the upper shoulder belt.
Alot of these cars had the second lower belt removed to reduce the clutter since most never used the shoulder harness anyway.