The article doesn't address straight axle set-ups. You can boil bump-steer on a straight axle down to one component - the drag link (assuming kingpins, wheel bearings, tie rod ends, and steering box are in good condition and adjusted properly). With the frame sitting as low as you will have with a 3" dropped axle and mono-leaf springs, the drag link will have a serious up-angle from the point that it connects to the pitman arm, forward to where it connects to the steering arm. To eliminate bump steer the drag link must be as close to level as possible.
I can't tell from your posts what year truck you have, but on some models a simple drag link "flip" at the steering arm will get you there. Others' have heated and bent the steering arm downward to get the drag link level (do your research on this one or have it done by a pro), you can also relocate your steering box higher on the frame with a simple bracket made from 1/4" plate. There are other ways as well, I would contact Sid, he's the expert on these set-ups, he can provide you with exactly what you need.
My 3" dropped axle and mono-leafs has zero bump steer, so I know it can be done.
