[Alan Roehrich]

The 8.1 doesn't really have 9/16" studs. It has a 3/8" stud on the bottom and a shouldered nut that goes through the rocker to create what GM called a "net lash" system, which in plain terms means "non adjustable".

The limit to how "square" a flat tappet cam can be is lifter diameter. A Ford with an 0.875" lifter, a Chrysler with a 0.904" lifter, or an Olds with a 0.921" lifter can generate more tappet velocity (what makes a cam lobe "square") than any Chevy with an 0.842" lifter, regardless of spring pressure. It does not matter how much spring, or how good a rocker you put on it, the lifter diameter is the limit.