Yes, this is a fairly common issue. Older Jomar/Moroso stud girdles were designed around standard SBC layouts, and Canfield 210cc heads often have slightly different stud spacing and angles, causing fitment problems without modification.
With 7/16” rocker studs, a girdle is not absolutely required at 7,000 RPM if the valvetrain is high quality and properly set up. However, a girdle does improve stud stability, reduce deflection, and increase valvetrain reliability at sustained high RPM..
