YOu can buy it once over the border. Don't know if the pits you select will be able to carry it there for you. Just put a crate motor in. The difference in fuel is 3-4 bucks a gallon. How many gallons you gonna need?
About 300 depending on mileage. I figure 4 mpg, maybe better on the highway. Last years race was 1300 miles including transit stages. My truck is dry sump and odd fire 4.3 V6 so changing it all around for a basic crate motor probably wont work. I have a complete full race motor disassembled that I was going to do 9.5 or 10 to 1 pistons but Its a time and money thing.
Mag 7 works with NORRA on pit support. Contact them direct, I'm sure they can support your needs given adequate advance communication. MAG 7 Home Bill Thompson is the head cheeze there.
Bill Rodriguez at Sunoco in Ensenada can sell the fuel in Ensenada. I have 619-247-1798 for Bill R.
Between Bill and Bill, I'm sure you can work out a way to purchase, transport, and pit all your high octane needs.
And if that does not work, please drop me a line a NORRA, firstname.lastname@example.org and we will see how we can make this all happen for you.
Last Mexican 1000 we used Mag 7 to do about half our fuel stops and my chasers did the other half. So my team had to wait half a day in Ensenada for VP race fuels truck to show up so they could pick up their fuel. I'm not blaming anybody at all, they were all cool. It is just SO much easier to use pump gas at a NORRA race. I know you're headed that way though...