Not sure what you mean by "stress relieving".
If you mean beefing up points of the chassis, such as suspension mounts, that recieve a lot of stress; Most of that is covered in the 600 Racing Rule Book. For the most part, the chassis must remain stock as recieved from 600 racing. Al posted a steering rack mount "how to" that may be helpful.
If you are running SCCA ,or some other "non-traditional" organization, I would suggest checking the rules first. I know on my suspension mounts, everything will be double shear, gusseted, etc... My car is also NOT Legends Legal. I will be running SCCA Auto-cross; and Everything that I am doing on my build, is only "Loosely" based on the Legends Car format.
I hope that helps you some. If you are going a "non-traditional" route; PM or email me. I'll be more than happy to share what I can with you.