There are moments at my age when you think just maybe your memory is failing. But rudiger’s comment on the ’64 Chevy 409 CC: The L78 (or L89 if aluminum heads) 396 was only rated at 425 hp for one year (1965) and then only in the Corvette. It was probably no different than the regular 375 hp L78 396 that was in everything else got me scratching my head, since I seemed to remember that the hi-po L78 396 was rated at 425 hp in the big Chevys too. Went to wiki, and they also said the L78 396 was rated at 375 hp, other than in the Corvette. Did I remember such a memorable thing as the 1965½ introduction of the new porcupine 396 wrong? At the impressionable age of twelve? Time to find a brochure.
Sure enough: 425 hp. Just the thing to power your new Caprice four door sedan, with the optional four speed stick. So the only question is: were there more or fewer 425/396 Caprices built than 140 hp 230 CID six-cylinder 1965 Imapla SS convertibles? Oh, and of course Chevy was just playing around with the advertised hp numbers: the 425 and 375 hp L78s were the exact same engine. But it wouldn’t have looked right for there not to have been a 425 hp engine on the option list. In 1966, the 427 inch version of the same state of tune was also rated at 425 hp; how convenient. Who knows how much they really made?