A method and system for aligning a component within a turbine casing, and a related turbine casing, are disclosed. In a top-on position, a location of a reference point and another, vertically spaced reference point on the lower casing are measured. After removing at least the upper casing, the reference points' locations are measured again, and the locations of a reference point on an upper surface of the HJ flange are measured. A prediction offset value is calculated for the component support position in the top-on position based on the locations. The prediction offset value may include a vertical adjustment based, in part, on a translation of a triangular spatial relationship of a number of the reference points and/or a tilt angle, a horizontal adjustment, and a HJ flange surface distortion adjustment. The component support position is adjusted by the prediction offset value to improve alignment.