The spec in the service manual is 1 to 1-1/2 lb with the sector adjustment completely loose and 2-2.5 lb with the sector adjusted at the center of travel of the wheel. Multiply that number by the radius in inches of the wheel (mine's out in my parts storage and not really accessible). That will give you the number of inch-lb you need.
For instance if the steering wheel is 18" diameter, then the right reading on a torque wrench would be between 9 (9x1) and 13.5 (9x1.5) inch-lb for worm bearing preload and 18 to 22.5 inch lb with the sector adjusted correctly.
Be sure to use the actual steering wheel radius, not my guess. 
Chuck, I used a fish scale as that's what I had easily available. Yes, a trigger pull scale would be more accurate.
