[750hp]

Seems pretty simple to me.

Option 1. Be a victim, b!tch and moan about the laws and policies, and worry about what might happen if you're pulled over and inspected.

Option 2. Assume that the engineer papers are long gone. Talk to a local engineer about having a new compliance plate fitted to ensure that the car meets the relevant ADRs for the year of first registration. Won't cost much money, and you'll have all the documentation you need. If the car doesn't meet relevant ADRs, make the changes required and you're good to go.

Seems to me that any interaction with Qld Trans or traffic police will start with one of two scenarios. Kick and scream about the system and you'll get reamed. Show that you have a reasonable attitude and that you're doing everything possible to comply (and have the documentation to support it), and you'll be fine.