These unique cars were built by individuals or by a team. The muscle cars on this site were built by one or two people.  The engines they put in the cars were powerful enough to drag race.  The import cars were made to race but maybe not drag racing.  The engines in the imports are differently made than the muscles.  The import cars add body kits and spoilers to add the look.        Classic cars on the other hand are made more for looks than racing.  Those type of cars are rarer to find that are in good conditions.  they are pretty expensive to restore.  There are companies that do this kind of work but you have to pay for the parts and the laybor so its evan more expensive.   
import cars  muscle cars   classic cars