91 Octane in a 340?

RustyRatRod said

If it's a stock engine compression wise, it's not a true 10.5. None of them were what they were advertised as. They all blueprint lower than advertised, because of taller than spec deck heights and larger than spec chambers. Its true ratio is probably down in the 9s so I wouldn't hesitate to run 91. If it rattles, you can always go back to the 94 but I doubt it will.

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The previous owner was far more knowledgeable and experienced than me, he said he ran 91 octane though he did not drive/own the car much before he sold it. He said it should scream on 94, but realistically I understand that if the car doesn't need it, it won't run any different and it's just a waste of money. 94 octane just provides extra Knock resistance. This 340 has a roller cam aswell, though that shouldn't matter. I know my old 360 with Aluminum heads and Keith black pistons in the Volare had some 10.5:1 compression, though again no way to measure. Sometimes it would miss in the upper registers and the power would Dropoff momentarily, so I guess this what I should be looking for?

On a side note, is it true that the 340 was pushing far more than 275HP in its stock form? The articles I read suggest that it was closer to 330hp, though who knows. I suspect with the cam I have, carb and headers I should be close to 380Hp or so.