Start with the functional length between the K and the LCA being the same as with the stock strut rods for the adjustable strut rod and work from there. You want the LCA to be perpendicular to the frame, and you want it to be free of any binding when it travels up and down. Adjustable strut rods are not for adjusting the alignment specs, although you may see a change in the alignment numbers after installing them. The goal is the free movement of the LCA up and down, while reducing movement fore/aft.
You'll want to have as much of the suspension installed as possible while still being able to check for resistance/binding. So, torsion bars in, UCA's, spindle, LCA's installed. You'll need to remove the torsion bar adjusters so you can cycle the LCA up and down by hand. You'll also need the shocks out, and if you have a front sway bar you will want that disconnected as well. Then cycle the suspension up and down, from bump stop to bump stop, and check for binding. If you know where in the range of travel your ride height is that will be better too, since you'll want that to be the neutral spot. It takes a little trial and error, especially the first time, to get a feel for what is normal resistance and what is binding. When you think you have it good, put another turn on the adjustment in one direction or the other and see what that does. If you're right, it should be more binding, if you're not, you may get less.
I've found with my cars that the adjustable strut rod ends up being a bit shorter than the factory strut rod, but I also use Delrin or poly LCA bushings, so the LCA may be slightly farther forward with that arrangement than with the stock bushings.