Looks like they raced Midget Sized Roadsters, never seen one before. Madis OHV must be rare, never read about them.
And here is a picture of a roadster with the Madis /Ford 6 OHV conversion. Looks like a Model T frame. Notice that the hood appears to be extended about 6” to accommodate the extra length of the 6 cylinder engine. This car ran at Carrell Speedway. Obviously with some success!
Probably Motorama at the Pan Pacific - https://www.customcarchronicle.com/historical-custom-car-shows/50s-la-car-show-memories/ https://laautoshow.com/history/