Is 9.7:1 compression on iron heads too much for 91 octane

The blueprint iron headed 408 that I bought said it was 9.8 to 1 and recommended 91 octane and had a warranty. I think you are fine.

It's not that simple. What's the dynamic compression on that engine? That engine also has Magnum heads, which are closed chamber for better quench. If the OP is talking about domes he doesn't have closed chamber heads.

And you'd better check the numbers, because Blueprint also says that engine is only supposed to have 34° of total timing at 3,500.

It's easy to say his static compression is lower so he should be fine. My compression ratio is 9.8:1 after all. But his dynamic compression is a lot higher than mine, and I still pulled a couple degrees to be safe because I run it on the street and don't change my tuning for every trip to the grocery store.