JW,
In doing a quick read of the steering box adjustment procedure in the Shop Manual, the Major Service Operations instructions describe "Adjustment - On Bench" and seem to indicate the pitman arm has yet to be reinstalled after removing the unit and rebuilding). That step isn't mentioned until after the adjustment process is completed and your are re-installing the steering assembly to the truck.
My guess would be you will be fine with doing the adjustment without the pitman arm attached to your connecting rod while the unit is still installed in the truck. The instructions in both the Minor and Major Service Operations "adjustments" both say your weight scale pull reading when measured at the steering wheel should be between 1 - 1.5 lbs.
Sounds to me like you are ok with what you plan. Just be sure to follow the steps specified in the full "Minor Services Operation" from beginning to end.
Dan
