I think the words "rat rod", is a 21st century word, coined by the latest class of people getting into cars. When I was coming along (back in the stone age of the 50's), they were Hot Rods or Customs. There were no "Street Rods" or "Rat Rods".
Most of what I see classified as "Rrat Rods", they have the old patina look, but billet engines and suspension, etc. In the 'old days', we did not want rust of suede paint, it was because that was best we could do at the time. We got rid of the rust and suede paint just as soon as we had saved up enough money to paint them. We did not take hammers and hit our car, or sand to metal and poor water on it to make it rust.

Jack