After removing the old lower seat reinforcment and remaining inner rocker fragments, I used a hammer and dolly to straighten the outer rocker flanges so I could test fit the new inner rocker and front torque box. Here's a shot of the inner rocker in position.
... and looking forward toward the new torque box.
... and from the front. It seems to fit pretty well and only required a small amount of "coaxing" with a rubber dead-blow mallet.
I next removed the whole lot and sprayed everything with a coat of Ospho, let it dry overnight to convert the rust to iron phosphate and then slapped on a coat of ZeroRust encapsulator paying special attention to the inside of the exposed frame rail and rear torque box.