Tom's description of what I did is accurate. I took a rotten 74 Sunbug down and "most" of a new Mexican Beetle back up.
Although technically you can bring in a non-complying car into Canada, I highly recommend against doing so. You will have to prove that you destroyed the chassis after you are done with it or there are stiff fines.
For me, crossing the border into the USA at AZ was no problem. To the customs officer I was not a US resident bringing in a potentially non-complying car.
When I got to the CDN border, all I was doing was returning in my "74 Beetle" Even with all the numbers on the car matching my CDN registration, it took me almost 2 hrs to get through Canada Customs.
The emissions numbers for Mexico are the same as for the USA/Canada, so it will have no problems passing any sniffer test. However, the car does not meet USA/Canada emissions standards since the standards here require that all cars have OBD II diagnostic capability. Emissions specs are the least of your problems if you think you can register it here as a 2003 model year. In the past you were allowed to modify your foreign car to meet CDN laws, but no more. They had problems with people not following through with the mods. For example, some cheap bastard wants to buy a new Merc Benz. He sees the price of a particular model here, but knows that they are $4-5K cheaper for the same model in Germany. So he buys the car in Germany and ships it over, only to find out he now has to spend $10k to upgrade it to CDN laws. So he goes crying to Transport Canada for an exemption. Finally, in response, Transport Canada had a law passed. If the manufacturer doesn't state the car meets CDN standards, you can't bring it in. No exceptions.
If you really want to have one of these cars, watch TheSamba ads. They come up all the time on there. Look for one that is built on an old German made pan that was registered in the USA for the last 3 decades. Buy it and bring it into Canada as an antique car (no duty). Any btlmex car is done this way. The biggest concern I would have buying such a car is rust. Find out if the car was driven through the last 6 Chicago winters or not. The Mexican factory made no effort to rust protect the cars since there isn't much rust in Mexico. If I were to buy such a car, I'd confirm the condition as best as I could, then buy a one-way flight and drive it home. This gives you the opportunity to back out of the deal if it is a rotten car. IMO, stay away from any car with an aftermarket sunroof. If anyone claims their sunroof was factory installed, they are wrong. All Mexican Beetles with sunroofs are aftermarket.