STEEDA 2005-2006 MUSTANG FRONT CONTROL ARM RELOCATION KIT

i assume that it changes the geometry of the front of the car, and that changes the center of gravity. similar to the rear LCA relocation brackets that changethe geometry for better instant center, etc.
 
That's correct. You don't need the kit, but it will put things in better sync by raising the control arm 3/4" to get the correct roll center relationship and it lowers the center of gravity. When you use Steeda springs it drops the car 3/4" and the kits bring that geometry back in check.