Shoot anyone can send a spec sheet in to any of the rod and piston manufacturers and get a set of stock sized forged pistons and rods for a decent price.
Oh and of course you dont have to leave the pistons and rods at the stock specs.
Ford also mentioned how important it was that they have a rod/piston combo that only weighed in at 1 kilo.
So of course trying to stick with that weight or go lighter will result in a change of the design.
This 5.0 article talks about it.
2011 Mustang GT Coyote Engine - 5.0 Mustang & Fast Fords