OK, I know what you are talking about, now.
Yes, most of them were a wavy or corrugated looking piece of steel, just behind the outer door skin. Most of the newer cars just have a sizeable piece of pipe in that location.
I can’t comment about F-bodies - but I have seen body shops replace a bent outer skin, cutout that (bent) reinforcement and slap a new skin back on. I asked about it and I was told “parts weren’t available” – but I suspect shotty workmanship (or lazy).
Actually, I will leave that as my last comment, otherwise IDK.