100 Octane with 12:5:1 340??

I have a 340 with 12:5:1 comp street car. What are the opinions about 100 octane gas ? Do you think it is sufficient? We have a couple of ststions in our area that sell 100 and 108 octane fuel and I have been experimenting with mixtures etc... I have run this motor a few times on 93 pump gas and have never experienced any knocking or pinging.