the back side of your rocker arms are hitting them at full lifte the make of your guide plate look thin to . they look thin . look at your out side of the stamp rocker and the guide plate were it steps up looks like it is hitting there i have had that happen on roller rockers had to go with long pushrods and i would get some gm guilde plates for the old mark 4 engines there are about 1/8 thick the ones you have look like mark 6