...per cubic inch!, not power.
A gen 2 hemi might make more power per cubic inch at 366, or 396, and that might allow a class car to run at a lighter weight (and launch better, as a result) but you are not gonna make more POWER with a 396 inch hemi, than a 572 inch version.
The old modified production cars usually ran the smallest practical engine for the weight class, cause the heads at the time could feed a 265/283 (272, 291, 301) at high rpm, much easier than a 350/365/383. The Fords ran the best heads they could find.... on a 221.