No rear overload spring on my new 2012 Ford F250?

250 only gets the upper overload if it has the camper package. You'll also find that you probably don't have the factory sway bar either.

The whole truck weighs 500lbs less is complete nonsense, quit peddling that non-truth. Whatever they saved by going aluminum went back into the drivetrain. I've owned very similar trucks across both eras and they have almost identical payload.