hi , The uk firm that built me a new radiator core for my F60 V8 radiator said that they lined old fuel tanks with a liquid sealant i think it was called" slosh" .strip tank, clean it chemically and then fill with slosh sealant then rotate tank side over side and end over end to spead the coating internally, then drain of excess, It dries like an internal skin. Have yet to take them up on offer. However i am told it is resistant to most fuels EXCEPT LRP [lead replacement petrol] as it eats into the rubber? content of the liner. Maybe some one who restores vintage cars near to you could shed light on the process and cost dangers involved and a firm in Aus who can carry out this type of work.
Our thoughts are with you all in Australia at this time. Hope the weather soon calms and the emergency services will be able to stamp out the fires.