I am looking for other opions on the subject of mixing leaded race gas (Torco Blue 110) and premium unleaded 93 octane. I am currently running a 66 GTO with a 400 at approximately 71 to 72 cc chamber volume. My heads are #62 castings that are highly ported with stainless steel valves and NO hardened seats. My compression ratio calculates to 10.2 : 1 I have read about other guys using only the Torco blue with mixed results. If I mix both types of fuels, what is a good ratio and should I use the "lead substitute" to offset the unleaded fuel? Thanks for your comments.