Thriller,10% alky is OK IMHO and it does pick up the octane noticably. It's when the percent gets higher than 10% is when things tend to go sideways. FWIW, my 1990-build 351-C has SVO aluminum heads, an SVO hydraulic flat tappet cam, Rhodes fast bleed lifters and forged pistons with a measured 10.5:1 C/R . Ignition timing is at 29 degrees BTDC. It runs without knocking on 91 octane pump gas. I've used up to 1/3 tank of 89 octane when forced to on the road, but I also don't hammer the engine with that stuff, & i add 91 octane ASAP.
Caveat- I'm also at 4600 ft average altitude and my Bob Oliver-modded Holley is jetted for it. Years ago we got 22 mpg over the desert to 'Vegas- and back (1000 miles) on pump premium with precious little travel below 90 mph, so it CAN be done without race gas & higher compression. Judy did an open-track day at Spring Mountain raceway without incident during that trip, too. You gotta pick your parts correctly & drive accordingly. NOT a race engine & way under 500 bhp!