Rebuilding of a Triumph T100 Valves Question.?

This bike has been off the road and boxed for years.When it last ran it was on leaded petrol. With the unleaded petrol of today do the valves need to be changed or do I need to use a fuel additive or just run it on unleaded. Any advise at this time would be most helpfull as friends seem to have different opinions.Thanking you