Not sure if this has been mentioned or not, but.... A Ford F-150 is still called an F-150, no matter what engine is in it. A Chevy Camaro is still called a Camaro, no matter what engine is in it... Etc.

The only difference should be what is currently used now: USAC Midgets, Powri Midgets, Illini Midgets, etc.
Simply goes along with everything else in the world like World of Outlaw Sprint Cars, ASA Stock Cars, All Star Sprint Cars, Badger Midgets, etc.
Never sell yourself short with a name. Just say what it is. People in the game will know what it is. The average fan may know what it is, and the family who heard an ad on the radio about a race, wont care what it is... They're just there to be entertained by the stars and cars of that particular series.
That is all.