How to import a classic car from Mexico

Stick with '94 and older vehicles and you don't have to deal with the EPA at all. You will have to work with a broker in the USA. They will know exactly what needs to be done to import to the USA. Obviously, none of this is free. There are duties and fees that the USA also collects on any import. You'll have to check with the Mexican authorities about their rules on exporting.
This might be a place to start: Importing Cars To The U.S. | Clearit USA