I did a search on this issue a while ago. Looks like it ia a pain in a... to make JDM car legall.

here a link to JDM used car seller in Japan. Click on "the Unated States" link there.
http://www.j-garage.com/imports.htm

It is known that it isn't that hard to convert RHD to LHD. All that you need is totalled LHD vehicle.