Fluidampr’s Ivan Snyder says that you should only consider the crank key as a mechanism for making sure the timing marks on damper are lined up properly. It’s actually the press fit between the id of the damper and the crank snout that’s important. Ideally, you want 0.0005- to 0.0015-inch of press fit. Before installing the damper, measure the diameter of the crank snout; a Chevrolet small-block should measure between 1.246 to 1.2465 inches. Although no damper manufacturer will recommend it, if you find the press fit is too tight you can have your machinist hone the id of the damper a few thousandths to get you out of a jam.