Mine was doing the same thing as yours, would not turn to accessory position. Then it sometimes would get finicky and not want to turn to other positions. I wiggled it around a little and got it to go into accessory position and then I inserted a paperclip in the hole and released the cylinder. I found the cylinder had partially fallen apart. So yours may have the accessory position, but the cylinder is having a problem. That's my guess.
http://67-72chevytrucks.com/vboard/s...d.php?t=720293
According to other posts on the forum, 67 and some 68 key switches do not have the accessory position, and you can remove the lock from the left-most position. Here's another thread about it:
http://67-72chevytrucks.com/vboard/s...d.php?t=648141