Not positive what your objective is. Are you trying to fix the head stock spindle taper or identify what it is? First off is there something wrong with the spindle? Does it have a problem from an accident? If the spindle in the lathe runs true the first thing is to identify the taper. Surely it is a standard unless someone has modified it. If you are trying to put it back to a standard taper you should find someone with a DuMore tool post grinder with accessory long axis slide of its own. They do exist and are used for truing precision machines after bearing changes. Been there done it! But the spindle taper should be where to start and go from there.