Hi Richard,
I have done several Pioneer runs (52 miles) on a 1913 2¾ on about 3/4 tank of fuel. I have also done the Banbury run when it started from Towcester racecourse on an earlier 2¾ with a smaller tank - again without running out of petrol. If you are worried about running out, you could strap a plastic fuel can on the rear carrier.
Regards,
Eddie.