Handling performance: most important chassis bracing/reinforcement - per application?

You may recall XV Motorsports did some real chassis modeling under loads. Some of the videos may still be floating around. IIRC the front end was the area that twisted the most when a front wheel was loaded. I think Pete Bergman worked there for a while. Peter also has track time so its not all theoretical. Maybe he'll pipe in with his thoughts when he sees this.

Closer to the other end of the spectrum from Mitch's ESP Challenger, check out cage work on Jess Neal's 'Cuda. Even includes bracing in the engine compartment.
‘Cuda to the Clouds