I've always thought of the Rat-Rod as a counter-culture approach to automobile styling. It's the "I don't care that it looks like crap, just as long as it goes like hell" attitude.
I wonder if the term is derived from the old hot rods and those true enthusiasts who live in the desert; those old grizzled non-conformist individuals who live to drive hard, even to the point of sleeping out on the old lakebeds next to their car just to get an early start on the racing. They won't spend any money on their car's appearance, only the engine. What we would call a desert rat.
For some reason the rat-rod should include red rims. Perhaps that's indicative of money going into racing rims instead of paint or damaged body parts.
I came across one of these individuals at a car show. He entered an old beat-up badly oxidized generation two convertible Corvette. Though it looked like it had been driven hard and put away wet, it looked like a machine not to mess with. With fat tires on back, lots of engine with definite modifications, lack of hood, serious roll bar and torn out interior there left no doubt the only reason for its existence was to go like hell. The owner looked as tough as the car; scuffed leather vest, boots with holes, skinny, grey stubble on a wrinkled brown leather face. He sat on the back of his car chain smoking and drinking coffee, not caring what folks thought of the car, oblivious of this butt-ugly vehicle sitting amongst restored classic beauties.
He looked grumpy like he had slept in the car. Maybe the ground was too hard. He didn't say hello. I took the long way around to the refreshment stand.