Heat treated frame?

[87wildside]

I am boxing my frame (87 S10) and making some x members with A36 hot rolled. I went with HR because from what I could find thats what the frame is made of. I posted this up in my project thread on another forum and received this response;

one thing that you might want to research is if the frames had any sort of heat treat from the factory to harden them or normalize them after welding, and you might want to research if your weld affected zone is going to hurt you at all

Would this be a problem? I have seen pleanty of boxed frames but now I'm worried about it.