The rear crossmember that welds to the back end of the frame rails on 1964-67 GM A bodies.

It's usually rusted and often bent from towing another car. Correct gauge steel as original.

It's probably much easier to weld in a new OE style brace than to repair your old one.  

Fits:

64-67 GM A body, GTO Chevelle, LeMans, Buick GS, Cutlass, Malibu