Have you ever wondered why the doors got heavier?

I knew from my years owning Camaros that around 72-73, the cars started gaining weight. The same happened to other cars including A bodies.
I bought this Ruster a few months back…..

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It was a 1974 slant six model but had disc brakes and some other parts worth pulling. It was way too rusty to save.
The right door skin was heavily rusted so I cut the outer skin to make it easier to fit all the hardware from it.
Check out this beefy side impact beam.

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I’ve never cut up a 67-73 door so I don’t know exactly when these beams were first implemented.
I just thought I’d pass this along.
Cheers!
Don't have any in my 70 Dart