I hope this info helps... it is an experpt from U.S. Customs Website:
Automobiles imported into the United States must meet the fuel-emission requirements of the Environmental Protection Agency (EPA) and the safety, bumper, and theft-prevention standards of the Department of Transportation (DOT). (Please see Customs pamphlets Importing a Car and Pleasure Boats.) Trying to import a car that doesn’t meet all the requirements can be a vexing experience. Here’s why:
Almost all cars, vans, sport utility vehicles, and so on that are bought in foreign countries must be modified to meet American standards. Passenger vehicles that are imported on the condition that they be modified must be exported or destroyed if they are not modified acceptably.
And even if the car does meet all federal standards, it might be subject to additional EPA requirements, depending on what countries you drove it in. Or it could require a bond upon entry until the conditions for admission have been met. So before you even think about importing a car, you should call EPA and DOT for more information.
Information on importing vehicles can be obtained from the Environmental Protection Agency, Attn.: 6405J, Washington, DC 20460, telephone (202) 564-9660, and the Department of Transportation, Office of Vehicle Safety Compliance (NEF 32) NHTSA , Washington, DC 20590. Copies of the Customs Service’s pamphlet Importing a Car can be obtained by writing to the U.S. Customs Service, P.O. Box 7407, Washington, DC 20044 or checking the Customs Web site at http:\\www.customs.gov. EPA's Automotive Imports Fact Manual can be obtained by writing to the Environmental Protection Agency, Washington, DC 20460 or visit: http://www.epa.gov.
Cars being brought into the United States temporarily (for less that one year) are exempt from these restrictions.
I do not think the links took well, so the main page is http://www.customs.gov/travel/travel.htm
and scroll down to the Automotive section.
Hope this helps.
76 240D - 550K miles
78 300D - 200K+ miles