After prepping the area, it came time to drill a bazillion holes for the bazillion plug welds all along the top and bottom flanges of the inner rocker and the various torque box welds. After I drilled the holes through which I needed to weld, I reinstalled the rocker/torque box assembly and then marked the mating side through the hole with a sharpie so that I could remove the red primer from the mating surface. I then removed the assembly, use a flat 3/8" drill bit to expose bare metal. Shown below are the exposed plug weld locations. I used a 3/8" flat end spot weld drill:
I then reinstalled the assembly and soon discovered an error. The front upper area of the outer rocker raises up in the front whereas the new inner rocker doesn't. This shows how the newly drilled holes don't contact the inner rocker:
Solution: I welded a 17"x1" strip of 14 gauge sheet to the front top edge of the new part so that I could weld to it.
That being solved, I carefully positioned the torque box and inner rocker in their final positions and then clamped them to the car in strategic locations including using a ratcheting tie-down in the middle of the rocker to pull it tight against the car in the middle (the blue strap in the image below:
Next came the meticulous task of welding. I would clamp between each weld point and use a body hammer to ensure the outer rocker flange was straight against the inner rocker plate with no gaps or wrinkles along the entire length and then weld one point and move to the next repeating the operation along the top and bottom. The torque box was actually tacked in place first and then the inner rocker and then the torque box was welded more permanently. No particular reason for not fully welding the torque box first, it just "felt" better to do it that way. Here's the full welded assembly:
Front the front. God, that's an ugly bead weld, I honestly thought I could do better than that. In this case the plug welds turned out better for a change.
Torque box to inner rocker welds.
Rear torque box to inner rocker welds. Next, I need to weld back in all the braces I've removed from this area that allowed me to get to the inner rocker as well as the rear torque box cover.