How to make torque boxes

Thanks for the comments. I actually used only about 1/2 of the $12.00 piece of metal, so material cost was about $6.00.

On the oval access holes, I used a ball peen hammer and a backer anvil made from 1/4" bar stock rounded over on one edge to form the flare. Clamped it in the vise and pushed the metal over.

On the E-Brake cable, this car had it routed on the other side (inside) of the frame rail so I think I'm OK there, but if not, I'll just make the needed holes and run her through!

On the frame ties, I got that off of Big Block Dart. Pretty simple, just a 2" X 3", 11ga tube laid flat. At the rear, the tube gets cut to lap over the frame rail, and has 2" X 5" flanges in front that get welded to the frame. Here is where you can run into issues with E-brake and fuel line routing.