If you have access to milling machine it is very simple to change taper. You don't even have to bolt down wheels as the counter sink will self center, just turn spindle slow, 100-150 RPM. Set quill stop so all will be the same depth. At most you are just taking off .040" to .050" to change taper. Much easier then modifying lug nuts, and you will not have to have special nuts if one is needed.
John