Originally Posted by hcompton
Is your car number matching to the 454?
It's a 64 impala, I don't think the 454 existed until 1970.
OP: Keep the 454. You'll end up happier in the end. Factor in the cost of a new torque converter and gears that you'll likely need to match up with the 350 and you could probably have enough in the 454 to make it a mean runner. It'll have way better street manners than any smaller displacement motor at the same power level. Like you said, no replacement for displacement.