I was stationed in Japan for two years. I really wanted to bring back a Skyline but the red tape was awful. The DOT(U.S. dept of trans) website has all the rules for doing it. Don't waste your time talking to the useless civilian employes on base.
The big issue is that it is a gamble (the reason I bought a 2001 vette instead). You can get a good deal on the Skyline in Japan. The Japanese hate used cars (well at least mainstream people do). Therefore used prices are much cheaper than we see on our cars in the USA. Also the exchange rate is really good too.
Let's say you drop $40k on a newer skyline. The only way to drive it in the USA is pay motorex, (Yeah right) or import it as a show and display car. As a show and display car, you don't have to modify it to be street legal. The catch is you may only drive it less than 2000 miles per year. (Does anyone else see this loophole...a few spare parts and like Lee Ioccoca said "She still reads 000"!)
My problem with this whole arrangement is trusting our F---ed up bureacracy with $40,000 of my possessions. If they decide to impound it, or declare it has a problem of some type, they can tie it up with red tape for months if not years. I believe the car will sit in impound for months anyway, plus however long moto-rex would want it for. All the while you are paying $800 per month in car payments for a car you aren't driving. Not worth the hassle.
It was nice to arrive in the USA pick up my shiny new 2001 Quicksilver Corvette Coupe and just drive it away. I love the Skyline GT-R and have really grown to hate Chevy service. However, even with all the service problems I have had with Chevrolet, I can't imagine the difficulties in trouble shooting a computer problem on the Skyline. I don't think Nissan would want to help (good luck)!
Trust me when you drop $40k you want to just turn the key and drive, not sweat the details. I will return to Japan in 2003 for another 2 year tour of duty. After that I may choose to try and bring back a used R-33 for $5k or so, but that is all the risk I would want to try.
Just my 2 cents.
Peace
Al