I would recommend a lead substitute such as Castrol Valvemaster, it is also worth using an additive such as Ethomix, this helps reduce some of the effects of ethanol in the fuel; it will not overcome material compatability issues. For more on fuel additives see FBHVC website also includes list of tested and approved additives.
Original oil would have been Castrol XL SAE30 or similar, this oil is still available, Morris Oils also do a suitable one. Do not use a modern multigarde oil, the detergents in it will wash sludge etc from engine and could block oil ways.