He needs to be more specific about a ST 60 case, there were over 6 different cases, He should post a picture of his, from all sides , and make sure he takes a picture of the rear of the case with the backplate off, There are many depth for the backplate, and some of the case took long or short plug in backplates, the cases where machined at the backplate seat so the plate would go in deeper or shallower
May also want to give the measurement of the sleeve bore, those varied too, as well as rod trough depth
Randy