Make sure everythings spot on ,timing ,valves and carb setup.Replace your points with Petronixs or similar,have a light right foot, 55-60 top speed and get there gently,definitely no roof racks.
Then the best thing I ever did was having an LPG conversion,Im paying 53p a ltr at the moment and I think its cheaper still in other parts of the country,but then you pay through the nose for everything in Cornwall.