It depends what issue is being caused.
If it's a noise issue, the 6-blade 'tropical' fan has a viscous clutch [14] which gets noisy when it gets older. New replacements are still available via Skandix, etc - p/n 1266788.
Seems to me like the 4-blade unit shown in [1] wouldn't have enough puff to deal with an OZ summer.
If it's an issue with overheating, and the fan shroud is in place and intact, it might be worth looking at the radiator and the integrity of the thermostat / cooling system, once issues like ignition timing, etc, have been ruled out.