If this is a 1979 Chevrolet Pick Up, there is NO Release Tab.....It is Held by a Screw:
Remove the steering wheel, as outlined earlier in this section.
Remove the turn signal switch. It is not necessary to completely remove the switch from the column. Pull the switch rearward far enough to slip it over the end of the shaft, but do not pull the harness out of the column.
Turn the lock to RUN.
Remove the lock retaining screw and remove the lock cylinder.
To install, rotate the key to the stop while holding onto the cylinder.
Push the lock all the way in.
Install the screw. Tighten the screw to 3 ft. lbs. (4.1 Nm) for regular columns, or to 2 ft. lbs. (2.7 Nm) for tilt columns.
Install the turn signal switch and the steering wheel