Tony, Sunoco 260 was 103 octane. Most regular was 91 octane leaded in those days. We ran Sunoco, Texaco and Shell in our hot rods. Sometimes we used Hess 101 octane. Sunoco 240 was 100 octane. All these were leaded. I run 93 octane in my 69 Z. A true 10.5 to 1 compression ratio. I mix that Jack Podell additive 1 to 1 with my gallons and NEVER have a problem. I am not sure that the Podell stuff is even doing anything. I just sleep better. I pumped gas for many years in those old days.
Sam