As you say Taps are OK (Tracy Tools).
In the case of the thread, a screwcut one is quite adequate, it does not have to be perfect, its job is merely to close the Register faces, the Register radial fit and the rear flat face are the critical surfaces which must be correct. Why would you need a die in this instance? If you are worried about thread form, do not be, merely round the crest of the thread for safety purposes.