Do you think they meant 574 horsepower and not cubic inches?
There have been numerous V8 Packard engines converted for marine use mentioned on this forum and elsewhere. They're mostly custom jobs, not even associated with one of the manufacturers who do marine conversions of automobile engines.
Jack, if you're really lusting for a V8 powered "vintage" runabout, how about taking a look at mine? Here's the engine layout. Quite clean, if I do say so myself:
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