Old men and old times that have thoughts only being kept alive in the minds of our elderly men whom grab up of the dwindling supply of old car bodies to build the vehicle that were the idols of their youth. A "Rat Rod" painted up to look nice or left with the body rust was the in thing. The Hot Rod and Rat Rod are two separate vehicles. The Hot Rod is any car fixed up to look great and go fast but the Rat Rod always has a custom exposed super engine dumped into an old car body. The Hot Rods can still be created today because all you need is to build up the existing stock factory engine with existing installed smog. The Rat Rods always have the stock engines taken out and huge horsepower custom built engines put into them built for drag racing ventures with the engine exposed and chromed for visual candy that can not conform to today's smog standards.
Building a "Rat Rod" from today's high bread messes manufactured is not impossible but difficult if you are not up on smog systems and DC electrical systems on cars. "It's The Law" that cars nowdays are equipped with smog systems and you "Can not" get your vehicle registered if that years smog system is not hooked up. Older cars pre 1968's do not fall under the smog laws and can be easily sopped up with a big horsepower engine with no smog. The smog systems after the 1968 were easily removed and altered until smog tests came to be. In the 1970's some states implemented various smog mandates but in 1984 you could not swap engines without the engines were smog compatible with the year model the engine was being put into. It's "Illegal" to swap engines from one car to another.
In the days of now complex DC computerized electrical systems control the smog systems and taking out the stock engine and swapping it out for an engine that produces a huge pullback when you stomp on the gas peddle is really difficult to do. With some vehicles if you disconnect any part of the engine wiring the whole car's electrical system will shut down so putting in a high performance engine would be difficult without changing the whole cars wiring system then you could not get the vehicle smog checked and registered if the new high performance engine did not have all the wiring connection points.
Used to be in the 1940's, 1950's and early 1960's you would be able to grab an old car body and dump a huge engine in it and go to the beach and do some cruz'in in a trashy looking rat rod that was cool. The days of ever building a "Rat Rod" out of your garage has come to a close or is coming to a close unless you have the cash to engineer a high HP custom engine to today's smog standards.
I see some painted up rat rods cruising the city I live in once in awhile that are 1920's and 1930's car bodies with massive exposed fully customized chromed engines. There's still some old junk car bodies around to do this but over the next 20 years or so the ability to find these old car bodies or even take a present day car body and create the "Rat Rod" will be impossible. Best you can do is take an existing model year car and remove the fenders and chrome the stock engine but I'm not up on the vehicle safety standards as of yet and most likely it will be illegal to compromise a vehicle's engineered crash safety.
Kiss the days of the "Rat Rod" goodbye. You'll just be able to drool over someone else's Rat Rod you see at a car show now or look at a picture.