you could probably use 87 for farting around town but as soon as you get into it...it will ping. Then when you get to the track you will have to use 110. So I'd try 89 1st then 91. You should be ok w/ that. FWIW I was using 93 on the 10.70ish:1 440-6. I only had the timing at 36* no problems. I was going to add 3 gallons of 110 at the track and bump the timing to 38*