I am going to throw something in here that may add to the confusion;
http://www.cbp.gov/trade/basic-impor.../importing-car
There is a link to A List of Nonconforming Motor Vehicles that are Eligible for Importation (By or Through a Registered Importer may be obtained from a RI or from NHTSA's website, about more than half way down the page. This link is a pdf that lists eligible vehicles.
The list mentions Canadian vehicles' age and their conforming to Federal Motor Vehicle Safety Standards (FMVSS). This list does not include vehicles imported from Japan unless those vehicles conform to Canadian Standards. However, there is a list of vehicles at the end of this document that includes a Nissan Skyline. I will let others read this to hear what they think of it.