I ran 11.6:1 in my 484 with no issues for years. I have a 605 hemi now, and I am right around 11.0-11.1:1 with no issues. The Hemi's are very resistant to having issues with detonation. I would be very comfortable running 12:1 on 93 and watching my timing and tune up. What we use around here is E10, so until they get rid of it, that's what I am running mine on.

I would not run any lower than 11:1 on pump gas with a hemi. If your building it, build it for 12:1 with .027 head gaskets, and switch to thicker ones if you have to.