A method of casting an assembly is provided that includes forming a structural insert, over-molding the structural insert with a temporary core, and positioning the over-molded structural insert within a cavity of a casting die. The over-molded structural insert is cast within a part, to form the assembly, and the temporary core is removed. The method may also include a temporary core configured to define an alloy flash trim location or locating features to position the structural insert within the cavity of the casting die. Further, the temporary core may define shared features with the structural insert. The part and structural insert may be dissimilar materials such as a part of an aluminum alloy material and a structural insert of a steel alloy material.