Open a blank part document (this works the same for assembly and drawing documents as well). Make all your changes in system / document options. Now save that blank file as a .prtdot (part template) in the directory it prompts you to. Save it with a file name that will make sense, like 'Fractions'. When you want to make a part/assy/drawing in fractions, just open that one up when starting with a blank file.
I'm going from memory here, but this oughta get you close atleast. People find this especially usefull when going from english to metric often. Or, I use to do modeling for another business and I have two different drawing templates; One with my business name and one with the other business name...both have the appropriate title blocks allready done.