Qa1 upper control arm and moog offset bushing help

I think the center of the ball joint would be in the same place regardless of its diameter. If you now have the smaller ball joint with late model spindles you have the adapter sleeves in the spindles. Change to the arms with larger ball joint simply means remove those adapters from the spindles.
My question is why in the heck would aftermarket produce upper arms that require something other than OEM replicable parts? Any brand of ball joint or bushing listed for a-body should fit in them.