Eric, if that doesn't make a difference, loosen the sheet metal locknut on the input shaft of the box, then back off the input assembly with a spanner about 1/16-1/8 of a turn.
When I did my cab swap my input shaft was rust pitted and leaked all the time, so I swapped in the input assembly from the donor truck. Before the truck was loosey goosey light steering and all over the road. After the swap it was a little tight feeling. I backed it off that much and it steers nice and smooth now. A few years later I was reading in the FSM and saw I adjusted it just like the book said to.