one thing that worked well for me was putting the axle under the vehicle with the axle and frame at where i wanted/thought ride height would be. from there i measured where things would conveniently fit and tried to visualize if i needed to move a mount up/down/forward/back, just how easy or hard it would be. THEN i went to the calculator... tweaked the numbers with what would reasonably fit, and got to it.
keep in mind the calculator is just a tool... designing something perfect in space and then trying to plug it up to your truck can be difficult, as fitment issues may arise. reverse engineering with the frame and axle in a fixed position would be how i would approach the build/calculator.