Ethanol in gasoline will destroy old gaskets and seals. As far as a lead substitute, remember that one of the purposes of the lead was actuallu to lubricate the valves. I have used one ounce of type A ATF per ten gallons of unleaded fuel for many years in my old cars. I got the advice from a column that Don Garlits used to write in the Detroit News back in the 70's or 80's.