The 427 that Roush makes is a stroked small block 351 based.
Their smallest and cheapest FE based (big block) is a 511 cu @ approx $29K US.
https://www.roushperformance.com/engines/511-srfe.html
Personally I'd try sourcing the engine in-country. If there are warranty issues later (chances are there will be) you won't be stuck with freight to-from the US.
I'd definitely lean on your Countrymen for advise and "been-there-done-that" experience.
From what I've seen Stateside looking at AU. The Smog laws are tough. The cars invariably are running Chevy LS injected, catted engines. What cars are running Ford engines are 4.6 Modular or 5.0 Coyote catted engines. I may be totally off-base though. Finding that 427FE big block Kirkam to the other day that I posted was the 1st street legal Cobra I've ever seen in AU with a Carbed Ford engine.