Rick you may get away with 93 octaine on an engine of 8.5:1 CR. Classic symptoms will be pinging and dieseling. An octane booster might make up the diffenence if needed. Good luck. Bob Ingman
You are worrying about nothing. My engine has 8.5:1 CR and I use only 87 octane all the time. I even ran 85 octane when I was in SLC UT.
No problems, no pinging.