In a word Yes. You will want to check with a Triumph Spitfire authority. I am only aware of one engine builders (Kohler) that prepared for the removal of lead from gasoline as far back as 1955. Lead in gasoline served as a valve lubricant on the pounding surfaces of the poppet valve face. If your engine builder did not anticipate the removal of lead there are some non-lead additives that can poured into your gas tank to provided the needed lubrication formerly provided by the lead. It is highly unlikely that a 1971 triumph spitfire engine would have anticipated the removal of lead. I am not aware of any automotive manufacture that had this much foresight.