What kind of fuel do you run?

I suppose you might have some options in Illinois. Here in California it's 87, 89 or 91 unleaded, all with ethanol.

If you have hardened valve seats installed, lead is not needed. Lead additives are questionable, anyway, because they tend to just sink to the bottom of the tank. I use 91 because the high compression 273 Commando insists on it. Some people make a big fuss over ethanol but I have never found it to be a problem.