Fuelling debate

I own an FE Holden with a ``Grey'' engine which wasn't designed for unleaded petrol. I use the car to travel to work every day and at 33 miles to the gallon it's quite economical, so I want to keep it. I have been told that a fuel catalyst which supposedly leaches lead into the fuel will enable me to run the car on unleaded. Is this correct? The engine doesn't use oil and is in good nick, so I don't mind spending a few bob on it. I have also been told it's possible to modify the cylinder head to enable the use of the new petrol. Is this right?. Is it also true that engine timing has to be altered to use unleaded and that this is not possible on all cars? What are the other alternatives if any? There is that much mumbo-jumbo going around about this subject that it's very hard to get fair dinkum info. Hope you can help!