I chose SRS from the list. I like the idea of GRS standing for Genital Reconstruction Surgery but I think that most people regard it as standing for Gender Reassignment Surgery. I agree with Polar Bear that the term Gender Reassignment Surgery is misleading, as the surgery does not change anyone's gender but makes their gender match their bodies.
However, I agree with treeflower and others that GCS, for Gender Confirmation Surgery, is the most appropriate term.