No leaded fuel. What to do?

["Jeff McNeal" <jmcneal@ohms.com>]

Back when I had my first Spitfire -- a '67 -- I had no trouble finding
leaded gas to put in the tank.  I just purchased a '69 and I'm wondering how
to keep this puppy alive on an unleaded diet.  My first inclination is to
simply fill it with premium unleaded, retard the timing slightly to avoid
pings if necessary, and take my chances.  I figure if it's still running
this many years of unleaded fuel consumption later, then I shouldn't be too
concerned.  Would adding octane boost to the fuel mix be advisable?