Julio,
There has not been any posting on this thread for a month. I do not know the status or outcome of your situation. Based on the assumption that you still have not imported the bus that you purchased to Mexico, I am reviving the thread.
Below is information from
http://www.apec.org" onclick="window.open(this.href);return false;
"•NAFTA allows Mexico to continue to restrict imports of used vehicles until January 1, 2009, when a 10-year phase out based on vehicle age will commence.
• However, the Mexican government permits limited imports of used vehicles from the United States into its "border zones" (northern border of Mexico, free zones of the state of Baja, partial zones of Sonora and the state of Baja California del Sur, and the border city of Cananea). Used vehicles from 4 to 15 model years older than the current model year (in Mexico, Nov 1-Oct 31) are eligible.
• In addition, a decree published by the Mexican government in its Diario Oficial de la Federacion on March 13, 2000 provides that beginning April 1, 2000, pickup trucks that were built in the United States or in Canada and that are at least 10 years old, may be imported for a fee of $200 plus applicable customs duties (zero as of January 1, 2003).
• Mexican residents must apply directly to the Mexican government's Commerce Department and Customs Office to obtain the necessary license for this wavier, as well as for imports that enter under the border zone provision. "
Now you probably know some of this and I suspect that the 'pahse out' statring in 2009 is for new US manufactured vehicles. It also states that the Mexican Government allows for some used vehicles 4 to 15 years older than the current year model. Your bus is certainly older than 15 years. I do see convoys of vehicles that have been purchased at auction here in the US headed to Mexico and they certainally have cars that are older than 15 model years old. I don't know if it would work to talk to these folks to find out if they are taking them through the 'free' zones into Mexico.
I am all for trying to do things legally by finding loopholes.
Thought...when was your bus converted? If the conversion, engine upgrade etc was done in the last 15 years that might be the basis for 'up dating' the year of manufacture of the bus. I know that I bought a 1956 model bus that the title had been changed to reflect the conversion that was done in 1990. I do not know how this was done as the person that I purchased the bus from purchased it this way from the conversion folks in Nashville.
I've also seen (read) that the State of California will legally issue a vehicle license to a non resident a current loophole in their system.
Let me know the status of your situation.
Larry