Legends car racing came out of this idea, back in 1991 at Charlotte Motor Speedway. They prepared some cars that were similar to the current Cup cars and were painted like how the participating veteran drivers' more famous cars looked (including numbers). After a meet-and-greet / autograph session, they put the drivers into the cars and out onto the 1/4 mile flat track that they'd made out of paving two narrow turns in the infield between the front stretch and pit lane.
They had some trouble with driver health problems, as well as some of the cars, so not all of the drivers actually raced. They also realized that getting these guys together to do this again would not be easy. Several drivers admitted that this race reminded them why they retired in the first place...
With the 1/4 mile track already built, and noting that stock car fans also liked the old modified cars, the brass at Charlotte Motor Speedway founded 600 Racing (now US Legend Cars) to run on it. The cars were supposed to be relatively cheap, easy to work on, and fit into the back of a pickup truck... of course like most racing series that soon got out of hand...