You are right about that. What you can safely run for compression is dependent on what you choose for engine components. My 383 has 10.6:1 static compression, and it runs fine on 92 octane. But I built it knowing that with aluminum heads and a CC Magnum 280 cam, I could run under 8.5:1 DCR which is the edge for pump gas. I originally wanted to run a CC XE274, but it made the DCR too high. Because the intake valve on the Magnum 280 closes 3 degrees later (66) than the XE274 (63), the DCR was lower and within pump gas range.