I'm sure they'd just make me pull the carb to check with a magnet if questionable. The rules don't say anything about stock cast, just cast. I'm pretty sure the majority of them are running non-oem cast iron. I saw the Indy cast iron heads, but their intakes didn't say whether they were cast or not. I'll start looking for the 71/72 intake. Thanks guys, definitely alot more info/replies than what I expected.