No, there were _major_ advantages to ethyl. It not only made high octane gas much cheaper to make, it made high octane gas _practical_ to make. Yeah, it's possible to make 90 octane gas from casing head, but it evaporates right from your tank and it's substantially less safe to transport.
Higher octane gas means higher performance engines for the consumer, and the consumer demanded that.
A side effect was the fact that valve seats lasted a whole lot longer because of the lubrication the lead provided.
And yes, everybody knew lead was toxic, but I don't think anyone had any notion just how toxic it was. Remember only 20 years before, lead acetate was a common ingredient in cakes and candies. On top of that, nobody had any idea that the auto industry would explode to the point where emissions were a big issue.
In retrospect, it turned out to be a bad idea, but I don't think you can blame folks at the time. For a while, you could buy gas with and without ethyl; they coexisted in the marketplace. But as I said, it's just not practical to make high octane gas without an octane enhancer. And the first convenient one that was found was lead.
I'd like to see a cite to that 2003 study. I'd also be curious if that study used an engine with modern hardened valve seats or typical 1960s soft seats.
Again, I have seen plenty of ads from the thirties promoting ethyl in gas, but I have never seen any of them promoting ethanol in gas. I'm not sure anyone ever knew about it in the general public.
Ethanol didn't make a comeback, though, until after lead was replaced by MTBE, and then MTBE turned out to be even worse than lead was.
--scott