I don't even know what to call this part I'm searchingfor

I'm replacing the floor panels on my 1969 Nova and I've hit a roadblock. I don't even know what to call this part I need, let alone where to find replacements. I'm just guessing it falls under "body" as it is a sheet metal panel, but it could just as easily be "chassis."

The part is the frame mount that is welded on the outside of the "toe board" or "firewall extension" as it is sometimes called. I'm replacing the toe board and I'm not confident I'll be able to keep this part intact (or if I even want to). The front bolts of the subframe mount on this body panel. Please end my suffering, tell me what it's called. And if you have any suggested places to buy it, that would be great too.

Thanks

maybe this link will help. http://www.shermanparts.com/

The part where the front subframe to firewall is called a front torque box [heavy bracket on outside of toe board]. The only way to get just the torque box is used... unless you buy a complete firewall

Thank you for your help geneo :)