I'm not so sure a 454 with oval port heads is likely to make 450HP. But I've been fooling around with aircraft for the last (undisclosed, I'm old) years.
Further, I don't believe most marinas sell high octane gas and therefore, the 450HP isn't coming from high compression.
Marine applications are designed to run at RPM all day and to do so, they're sometimes detuned for service life and fuel burn.
Yup, just opinions.