Interesting thread and I can give some input from an original Dodge lightweight I had several years ago. Unknown to me at the time it was once owned by a famous racer from CA. and was supposedly a national record holder at one time. It came to Texas in 66 and is still here as far as I know. My car was built on 4/05/65 and was built in one of the last bunches of cars. It had all the original lightweight sheet metal expect the hood, which had blown off during a race. I still had the scoop. My doors had all the inner structure under the door panel cut out so I investigated how to fix it. Now, my core support area was pretty badly bent from stress. I measured all of that area with a mic and it measured .018 in all places I could reach. It was very flimsy and noticeably thinner than my doors, scoop, and fenders. My fenders measured .026, as well as my inner door structure. I am convinced that my doors were original. The brace at the front of the door where the hinges bolted to, measured .036. I measured an OEM standard door and it measured .036 on the skin and .045 on the braces. I never removed my fenders to measure the structure or mounting places where it bolted to the inner fender. I never stripped my doors of paint but I could clearly see signs of acid and corrosion. The door frames that held the glass in were rusting from the inside out. It is dry here in Texas where this car has been all but one year of it's life and it was a 100% rust free car otherwise. You could also see one of two spots where it appeared that the acid and had eaten through a thin spot created by the stamping process and had been carefully brazed over with brass. I sold the car unrestored and it was " restored " by a guy in his backyard. He told me some of the things he had done in the "restoration" of the car and it made me shutter. So the history is all but lost on this one.