I’m so glad you brought this thread back up. This is where I first saw your spindle and got me thinking about it myself. That rotor is big, which one is that?
The S550 hub actually pulls the wheel mounting surface in about 7/16". I am sure I could push it out some and get it closer to stock, but it would probably make the spindle heavier and it already weights more than an F-Body spindle (if memory serves).
I think I could push the UBJ up about 1", but dropping the lower balljoint becomes an issue with wheel clearance pretty fast. It's one of the reasons I (and others) have stepped up to 18" wheels, those can use much wider wheel and more offset. It's really the only way to fit a bigger tire under the front and keep it in the fender. So dropping the LBJ compared to the hub would start to reintroduce that problem pretty fast.