I'm not sure about your local laws, but I doubt you can register and insure a dirtbike for the road anymore. You used to be able to do it, after you jumped through enough hoops, but all that's changed in the last few years (thank California).
The good news is, there may be no need. KTM makes a completely legal version of the EXC 450 or 530 for sale in Europe and they are most likely coming to N.A., if they aren't here already.
Husky already has their road legal dirtbikes available, and they are real, live, honest-to-goodness dirtbikes with lights and plates, not dual-sports, just like the KTM's.