Lead Additives for Older Outboards?

[spoggy]

So, my 1971 1350 Merc was built before unleaded fuel became the standard, not just an anomaly. It was seriously before ethanol additives as well. For all my older engines, I've sought out ethanol free fuel and use it religiously. I also like sta-bil. What about adding lead back into the fuel as well? The whitepaper on the 71 1350 advises that the spark be retarded a few degrees with unleaded fuel. Is there any real advantage to adding lead back into the fuel?