Hi , ive recently bought a 1972 Triumph Spitfire , ive been told shes had an engine rebuild and is now kitted up to run on unleaded , however there is no paperwork to back this up , the engine has covered 97K , doesnt look like its been rebuilt but a compression test at a garage 2 years ago showed a perfect 150 across all four cylinders...without stripping her down , is there anyway of telling which is the best fuel for Her?...thanks