That really isn't how it works. In higher energy interactions you'll do much worse in the older cab, because of the lack of functional crumple zones.

I've seen plenty of crash test videos of older cars just completely fold up the cabin (crushing the people inside) in a collision with a modern car. I imagine a 70's or 80s suburban crashing into a modern-day Camry, the people in the Camry would probably have a better survivability and lower rate of injury than the Suburban despite the size differences. Old cars just weren't built very well.

No, in cars built before we started paying attention to passenger safety, YOUR BODY is the crumple zone. If a tough steel body doesn't deform to absorb energy, that energy has to go somewhere, and will find the squishiest thing to dump into, which is you.