http://www.nhtsa.dot.gov/cars/rules/import/

That should help.

Ben 87 GL
http://pages.infinit.net/eurokit/

the following is a post i found on www.westfalia.org

Watch Out!
The worries are not worth the troubles in importing Westies to the U.S.
from Canada ( & Bugs from Mexico). I recently imported my dream 1978 Westy
in the spring of 2001 from BC to the US, it can be a confusing process but
if your "customs savy" you should have no problem. Even if you want to pick
it up yourself and drive it across the border the process has to
authenticated so it can be registered in the States.
First, before you even put an offer down on the Westy you should speak to a
Vehicle Import Broker. This person is who you have to go through to take
care of all the environmental standard, authentication and paperwork, and
also coordinates with your Importer who you will meet at the border to pick
up your private commercial manifest that you will give to the Customs
Officer upon entering the US.
Also their are alot of Catch 22's and red tape in vehicle importation
politics. It's how country's can make a little cash$ on the side. For
instance, if the Westy your interested in is 25 years old or younger it
must compy to Dept. of Transportation standards here in the US. Like a
metric speedo is against the law here in hte States. It must have either a
dual KM/MPH or a MPH only. IT MUST BE CONVERTED BEFORE ENTRY INTO THE
STATES! Also Canadian and Mexican Emissions Laws are more laxed than they
are in the States, Yes Canada has laxed emissions laws! So if its a smokey
pipe it won't pass here and therefore you will not be able to licence it in
the states.
Also, beware! i heard that the US is supposed to impound cars for a month
if they are not up to "American" standards, So please have all conversions
done before you go.
And one more thing! you also need to know the month and year your Westy was
made before you can even think about importing it from wherever!