THE short answer is there is no simple way of checking. Pre-unleaded cars had a larger fuel filler, and to avoid owners accidentally filling their cars with leaded a smaller fuel filler neck was used on unleaded cars, which mated with the smaller nozzle at the servo. Though the alloy head had a valve-seat insert, it might not be sufficiently hardened to cop the pounding from unleaded fuel. I also doubt Ford would have changed the valves to the hardened ones needed for unleaded fuel. All this suggests you shouldn't run the car on unleaded without an additive.

DRIVING around Australia today is a very different proposition to what it was in the 1970s. The roads are much better, communication has improved out of sight, and there are more dealers and service agents on the route you're likely to take. Back in the 1970s you went in a big Aussie six because they were tough and unlikely to break down. They were also easy to fix on the side of the road, and parts were relatively easy to get in the middle of nowhere. Today, if you're sticking to the blacktop, I would take a Commodore or Falcon and there are plenty available within your budget. But if I were going off the beaten track I would think about a four-wheel drive with its higher ride height for ground clearance, its ruggedness, and its drive system. Early Nissan Patrols, like an MQ, or early LandCruisers would be good, reliable and tough transport.