After rereading this post, all these months later, I remembered we had an 80s 5th Ave that originally had bracing that went from the center of the inner fenders to the firewall pinch weld, about 12" apart, 6" or so from the center. They were bolted into place on both ends. Usually these were in the way when you wanted to do any under hood maintenance, and were often removed and pitched. They were about 3/4" thin walled tube (think 1/2" electrical conduit) with flattened ends with holes for bolts at each end. I believe I remember removing them from a lot of Dusters, and some mid 60s B bodies!

This info is probably old and useless to the OP at this point, but it may be of interest to someone. Gene