Exactly. Your geometry is WRONG. I can’t say it any nicer than that. You are arguing a point just to be right, and you’re not.
That head has a taller stem height than a 273 ever had. That changes geometry. Are you running .450ish lift? If not that changes geometry. The stands on that head haven’t been relocated for your stem height and lift. So your geometry is wrong.
I’m trying to help you and keep you from doing damage to a rocker that doesn’t need it. Almost never does a rocker need to be ground on. The book you are reading is wrong. Don’t grind them. Call Mike at B3 racing engines and talk to him.
It’s criminal how many rockers have been junked from grinding on them. It’s criminal that Chrysler guys put up with geometry issues where there is no need for it.
b3racingeninges.com has 4 tech articles on this very subject. Please take the time to go read through them and then call Mike and let him help you. Your rockers, valve train and engine will thank you for spending the time to fix your issue.