From what I've gathered, what octane you'll be able to run will depend on your Dynamic Compression Ratio.Which brings up another question. I ended up with 9.92 CR. I will start this thing off with 93 octane, but was wondering if I could possibly run 89 with this combo? I really don't mind running 93, but 89 would be nice.
Something that I read on the subject suggested that above 8.5 DCR with aluminum heads is where you'll start getting into detonation territory.
So it depends on the cam that you're using. Later IVC lowers the DCR, and vice versa.
I don't know what DCR range would allow you to use 89 octane.
Get the IVC @.050 from your cam card, and put that and the rest of your parameters into this calculator to get your DCR.