[400TT]

The earliest you can run that has any hope of passing emissions is Falcon AU series if sourcing one in Australia. The best of these is AU3 as they had the most power, built by tickford and had some nice gear on them. Next best is AU2 which had a little less power but still had Tickford units available. Tickford units will have Tickford build sticker on rocker covers and tickford logo on throttle body etc.

From the USA the earliest you can run are any of the injected 5.0 HO engines. The best of these are from the early to mid 1990's, i.e. the last of them.

Forget any of the E series, they will not comply.

Forget any crate performance motors, they will not comply. Only rebuilt factory engines, rebuilt to original factory specs will comply.

The only exception here is that there are performance head, intake and CAM packages out of the USA that are also emissions compliant. e.g. trickflow, edelbrock etc.

Hope that helps.