Depends on the company really. There are a few good Jap companies with great reputations which a couple of my friends have imported high powered Skylines from, and had no problems even after a few years of running.
I'll try and find out who they were.
edit:
The company one friend used was http://www.draganddrift.com/index.php
It took 3 months for delivery after payment, and he was given a full spec list and tonnes of pictures before purchase. As far as I know, they are pretty reputable company. If you'r serious, its best to contact them direct and they may even be able to source, or build you the car your after.