Had a chat on the phone to a helpful lady at the RTA who helped as best she could and said they held records since about 85 which is interesting. I can get records that pertain to my ownership if I go to the RTA with ID, but they don't cross over with ACT so I will have to contact them to find out what they can do. She didn't seem too sure as to being able to contact any subsequent owners and said in my case if the car hasn't been registered for a while obviously it becomes more difficult till it surfaces again for rego.