At the bottom of that page is a diagram - that's the best way to look at it.
From the front of the car, look at the spindle. As it goes up and down, it travels in an arc. The upper and lower arms both travel in their own arcs, but because the spindle is attached to both of them, and they're different lengths, the steering arm travels in it's own arc. The tie rod has to be adjusted so it will exactly match the steering arm's arc.
In reality, the steering arm travels in an eliiptical pattern, not a true arc, but the tie rod DOES travel in an arc, so you can't adjust it perfect, only very close.
If you look at the longacre diagram, notice that if you raise or lower the rack location, the width of the inner pivots needs to change, as does the length of the tie rods, to match the intersecting lines. You only need to be close, so don't worry about custom-width racks and stuff, just take care in measuring the bumpsteer with what you have, and then adjust something and check it again. It only takes a few tries to get a feel for what's happening and then you can make smaller and smaller adjustments until you're as close as possible. For the most part, you're probably not far off to begin with, and chances are your only option is to adjust the height of the outer end, so you won't have much trial to get it whittled down.
It's kinda like adjusting carb jetting - make a single change and see what happens, then go from there.