Okay, I've found a 75 Cadillac fleetwood, {not a limo} in the junkyard with a 472. Now, I've read that the early versions had either 10:1, or 10.5:1 compression, and about 375 horse-525 torque, the mid 70's had about 8:1 compression, and about 220 horse-300 torque. I've also read something about swapping on a set of 425 heads to bump up the compression. My questions,
Do you think the 425 heads will give me the 10:1 compression, and could you run it on 93 octane?

Any input is appreciated.