But, I was speaking of the major open wheel circuits, like F1 IRL and Champ. Can you think of any of those drivers that have had real success in NASCAR?
That's pretty weak. USAC is THE open wheel sanctioning body in the United States. There's only one reason drivers leave open wheel to come to NASCAR, and it's not the racing: it's the money. If NASCAR runs short of money, these guys are going back to open wheel.
If you want to look back a little further, to when the different series allowed more switching, there are quite a few open wheel drivers that had success in NASCAR. Foyt and Andretti come immediately to mind.
Also, I think you'd lose this bet. I'd say it's closer to 50/50 between guys coming up through USAC on one hand and NASCAR or ASA on the other. 50/50 might even be high.