Jeff,
Unfortunately there's not much chance of being able to register a Cobra with that engine in Australia. I've got a BB Chev in the back of the shed and was planning to run it originally.
Our emissions and registration laws require an engine that meets the current emissions regs for new cars. Even though it's a replica of a 1966 vehicle the authorities consider it a new car and it must meet all of the registration requirements of a new car.
You could run an older design engine provided you could get it to pass the current emissions regs but it's very expensive to get an engine tested and certified. This puts it beyond the finances uf of us meer mortals. Robnel went through this procees to get the 429 BB Ford certified with their 8TB injection and Motec ECU but it cost them a lot of money. Also the Emissions laws change at the end of this year to the even more stringent Euro 3 spec.
If only the Cobra had been built before 1958 then we would be considered a Hot Rod and under a much more lenient set of rules.
Cheers