I would never buy interstate unless its something worth its while. I got a car 4 weeks ago with lots of mods from nsw and I am still having trouble with regency been twice.
Ive never heard of having a road worthy in SA.
I insure with just cars and they have never asked for that.Who told you that?
All you need to do if you buy local is fill out the green slip thats with the rego and take it in to rego office and change ownership.
No need to take through regency if you buy local
P.S buy my car