I've got a 64 bug I'm in the process of restoring/modding. I can't find any info on whether or not it needs to comply to ADR specs. All I can see is ADR apply to cars built on 1 Jan 1969 or later.

I'm not planning any stupid/dangerous stuff, I just need to know if I'll need a mod plate or not. Anyone know? I'm in QLD by the way.

You won't need to comply to ADR but you will need mod plate / engineering for anything you change
If you put Recaro seats in, then that would need to be plated

Awesome. That I can handle.

If you are staying stock and just replacing rust and repainting then you do not need too.
I personally would not drive a car without seatbelts however if I had the option so it is worth thinking about them.
I did not get mine engineered to start with. I will now.
In that case you need the adr stamped belts from places like the Busstop or direct from the manufacturer.
Then a engineering plate costs about $120-300 depending on where you go.

Seat belts, disc brakes and new seats are on my list. Possibly 6 or 8 point cage too. As well as an engine swap. And just upgrading all the old stuff I find newer gear for.

Be real careful with the cage. I would definitley consult your states appropriate engineer plate/ report approval. You wouldn't want to weld it in and find you have to take it out.