Nah they could have also stepped up by making what they were allowed to use, work better for them, just like the manufacturers they were chasing. That's how the small-cube turbo crowd got so far in front - they kept making innovations, while the local V8 crowd stuck with 16-valve iron V8s, putting them in heavy cars with comparitively primitive suspension and then complaining when they couldn't keep up.
Point taken re the Falcon/Commodore not being an international car, but surely they could have used some of the high-tech bits from their parent companies' overseas models.