I ran a similar set up as yours in my 69 elcamino with 10:1 compression and was able to run 92 octane pump gas with no problem. I was even running cast iron heads which are more prone to detenation than the aluminum are. That elcamino ran like a bat out of hell, alot of folks sure didn't like being beat by a truck. I got accused of having nitros all of the time.