remember,the goal is just 475hp
That doesn't seem a lot these days, but it was a lot more than engines were designed/rated for 60 years ago.
You have to look at the loading, hp, rpm, etc., but you also have to look at fatigue stress that's been in place over the last 50-60 years. The rods are also just not as rigid. Most guys that only had factory rods to play with and were turning some rpms had to machine the big ends out of round so that they would have acceptable clearance when running/loaded, to keep from spinning bearings.
For the guys that build for a living here, with our names on the engines, when a 450-500 hp FE bracket engine comes in, we're not going to take the liability of using a factory rod.
If you add up the costs of putting a $70 set of ARP bolts in, having them resized, rebushed, then sent out to be shotpeened, you're not going to be that far away from a set of Scat rods and just a little bit past that for a set of lightweight Molnar rods.