that is a great story

great to hear first hand experience vs. all the hearsay
Legally, you can bring in anything 25 yrs old with the appropriate paperwork. Really just comes down to the port and the agent involved as to the level of hassle. In my years of importing diesels, I had far fewer problems declaring entry in LAX than the one time I decided to declare in Raleigh NC. Those guys opened everything and delayed my shipment and I simply chalked that up to being bored and never having seen the sort of thing. LAX gets loads of traffic, and they just didn't have time if it wasn't full of drugs (my guess).
I believe registering it is the same deal outside of California. After my diesel swap, I simply walked into the DMV, which is run by contractors there, and said my title is incorrect, it says gas and my truck is a diesel. Really? Can I see it? Sure, I'll walk you out there... That was it. They called Raleigh, said it was diesel, and I got a new title right there.
Importing right out of Japan is really no big deal as long as you're willing to: A)Send cash to someone on the other side of the globe to buy something unseen and hope they are helpful to get things loaded B) Be prepared for all kinds of fees on both sides of the ocean C) Fill out some paperwork
D) Risk a big storm where your container falls off the ship and you lose everything E) Nobody caring about your stuff. Expect it to be sifted through on either side of the ocean.
I helped my neighbor bring in one of the first M3 Evo II's ever imported to the US and it came out of the UK. Easy peasy.