Your problem is in your first few sentences- - - -"Firestone"! I do warranty and damage claim inspections, and a huge number of my assignments involve claims against Bridgestone/Firestone stores. Find an old established independent alignment shop with someone there who knows enough about alignment theory to make your truck steer properly. Who did the installation of the new components? There are several possible ways to assemble things improperly that can cause the symptoms you're describing, but an experienced front end man should be able to spot that kind of thing right away. BTW, the "manager" (who is actually a salesman) is right about the camber adjustment procedure. That's the way I taught it for over 30 years.
Jerry
