What the most hp anyone has seen someone make with the stock cast rods in a 5.7? I'm just curious to how much they can hold.

I have made ~380 at the wheels in a Ram truck N/A. I have seen 400+ at the wheels on nitrous or boost. Not many rod specific failures, but the stock pistons are junk and failure prone.

Fail under just N/A? Or do they fail with boost/nitrous applications?

We have seen broken pistons (ring lands) on stock N/A motors.

There have been guys running 200 shots of nitrous on stock 5.7L bottom ends. The rotating assembly seems real tough other than the reluctor wheel and the piston/high ring lands.

My truck has been putting up with around 450rwhp for a while now off a 125 shot of nitrous. I used to run a 75 shot and it took that like a champ as well.