What's this part called?

ACME SS said

On Mustangs they are called Monte Carlo bars I believe. I'm guessing they were added to conform with goverment crash test or something? I'm pretty sure that should be a solid rod and not a tube smashed at the ends.

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I remember removing them from my original 75 when I pulled the engine, And I'm almost positive they were hollow. That said, I think a bit of properly dressed steel channel would be an upgrade, if they are in fact some sort of crumple zone piece or anti-body roll brace.