I worked for a shop for a number of years, we rebodied a number of cars. If your body was rusted out and we had a parts car with a solid frame. We never took a vin to sell to a customer though (no money in that). If that was illegal... all I have to say is "Oh well, didn't know then, not hurting anyone and if you don't tell the DMV they won't be any the wiser."
Swamp your vehicle? Really? It floored me when I thought of it! I thought that was crazy funny.
And as far as the legality of my own Dart. Quote me a law or regulation that I'm in violation of. I think you will be rather surprised with what you can have on the road.