I believe Rohn Moon did most of his winning in the 90’s. If not, he can correct me.
In the 80’s the big money 4 cycle open races were won by Robin Bradshaw, Charlie Sox, whoever ran and Enik motor or an Otis motor or a George Owenby motor. Dicky Wilson won several also.
I was spending my time on the west coast and pursuing IKF Duffys, etc. We didn’t have many money races out here. We did have one pretty good money race up in Vegas though. Ronnie Emmick won a bag filled with 1000 Susan B Anthony silver dollars. I believe he still has it too.
To me, dirt oval karting died when the drivers layed down, all the body work went on, and tire prep took over. Combine that will slow as slug motors and you have single file, follow the leader type driving. For asphalt sprint racing, that died when the shifter kart, TaG motors, Rotax and everything “Spec” came along.
I would bet $$$ that if the sanctioning bodies would each promote one class for fully modified 2 and 4 cycle to compete in, their Grand Nationals entry list would grow by leaps and bounds. And when that class pulled out and onto the track, Everyone would be watching. Basically, put on a UAS series on asphalt sprint tracks. It would certainly bring back the guys who enjoy tuning engines and karts.