Yep, no ethanol-free gas anywhere near Chicago. ALL grades now contain ethanol.....87, 89 & 93 all have it. In my opinion (chemist at automotive chemical company that manufactures fuel additives), ethanol doesn't hurt anything. Now, I've heard that METHANOL can be corrosive to some components of a fuel system, but not ethanol. Newer gas doesn't hurt the older engines as long as you have hardened exhaust valve seats ('71 & up cylinder heads - 906's aren't hardened). Lead used to protect the softer metal valve seats in the old days.
For the second half of your question..... all (or most) fuel additives can be used in premium gas that contains ethanol. What type of "additive" do you want to add to your fuel & what do you hope to accomplish by adding that additive?