Early 72 340, is this one of the de-tuned ones?

Can you elaborate on that. Why might I prefer a lower compression motor for my car?

Do you like sitting in traffic during heat soak and then detonating badly on acceleration? If so, go ahead and run 10.5:1. It's not my car. You're gonna hear all the forum heroes talking about quench and this and that.......but the safest thing to do is run a compression ratio safe for pump gas for a street car. I think the formula is for every 1 compression point, you gain 3% in power. IMO, that's not enough to risk engine damaging detonation to what could be an otherwise nice build.