Ten points and a gold star to John Sandoval for this tip!! I planned to tap the bottom of the shifter and thread in a grade 8 hex bolt with the head rounded to duplicate the original spherical knob, but moving the retainer pin is much easier. Now if we can devise a way to increase spring tension on the shifter so it detents more strongly to neutral, we will be all the way home.
Just another example of why this site is the best.