You don't understand. The Magnum heads have 5/16 holes. That's why a standard Chevy 3/8 stud won't work. The Crane kit has studs that are 5/16 on the head end and 3/8 on the rocker end. That allows you to use a rocker with a 3/8 stud on the 5/16 style head. Of course, like I said, you don't want to have a lot of spring pressure. I have the same cam in the RobKat motor that you have in yours. Nice and mild and easy on the valve train. As long as the OP isn't going wild, he can use that kit just fine.