I would not at all go to the point that 10.0-10.5 is of not any use in a 455. There are just to many factors to narrow the compression ranges in a chart like that, to me the higher octanes on the list are getting to high with respect to the lower octanes, ranges look to wide for the 87 and the 92,93.
I did a SR cam 9:0 462 with ported D ports that wants 91, I think it is borderline in some conditions to want 93, he is gunning for 10s 1/4 mile. Even though it is 9:0, you would swear it has 11:1. IRC, I think I have less cylinder pressure on my 461 at 11:1 than he would have. He is going after all the mid range he can find to launch his car, wants to drive it to the track. My car is a semi daily driver and I wanted efficiency @ low rpms, not a huge mid range, or crazy low end tq, but strong power up high. All things I did so my 4 speed would have a longer life. Complete different combos, same CID, 2 points different on SCR, basically the same octane.
FWIW. Power is in the heads. Compression more for efficiency. As long as the compression is adequate for the chosen cam, there is much more power with better head flow than compression. Nothing wrong with 9:0, depends on the rest of the combo. Not enough info in this thread to begin to determine where the perfect SCR should be. If in doubt, stay on the low side and sleep better at night.
