I am working on restoring a 1965 Bonneville,389 with 4 barrel, 10.5:1 compression. One of my paramount concerns is fueling the thing. I have done a lot of searching and have yet to find a definitive answer. The question is not correct octane, I can get AKI 93 at a local Cenex, but the question is additives or no additives. I have heard all sorts of things, ranging from "Don't worry, the valve seats are already hard enough, you don't need lead/additives" to "You should run down to your local airport and fill up on 100 Low Lead" (which is technically illegal), with all things in between. Should I replace the valve seats? (which isn't cheap) or are they indeed hard enough to run Unleaded, or will a bottle of fuel additive per tank be sufficient to protect the seats? Or possibly a Mix of AVGas and Unleaded.