Prior to the introduction of the "unibody", these old car frames were made of heavy guage metal. In my time I have seen many of the '54, '55 & '56 Ford front crossmembers rust-out but that part is made of much thinner metal. It gets it's structural integrity more from the way it is formed and welded together rather than having the piece made from heavier guage metal. That piece was a factory recall for replacement and folks are still replacing them today.
I have also seen one frame rust out where the rear spring shackle bracket is riveted to the bottom of the frame, and that can be repaired also by cutting out the rusted metal with a torch and welding in a piece of structural angle iron, then drilling holes for the two bolts that hold the bracket on to it.
I talked to an old guy who told me he had a '55 that had the crossmember under the engine rust out at the bottom. Si I said to him, ummmm, you mean the front crossmember? No, he said, the one under the engine.
That's real hard to believe since that is the heaviest metal on the entire frame. It is made of heavywall pipe, probably 1/4 inch wall thickness. Seems impossible that it would rust out.
if you do swap car frames, it is necessary to re-register the entire car with the vehicle identification number stamped on the car frame that you are using by law. I'm not sure if you need to also swap the identification plate on the windshield pillar.
Bear in mind, a 2-door sedan car frame does NOT have the 1/4 inch thick frame stiffeners welded to the bottom of the frame under the doors like the Vicky frames have.