A while ago I noticed how few European cars made over 200hp during America’s horsepower wars. Now, one could argue that European cars were rated more conservatively compared to America’s gross ratings, so in most cases we can assume American engines are rated about 20% too high (on the other hand some engines were underrated so ¯\_(ツ)_/¯ ). This list spans the peak of the power years from 1960-73, for after 1973 check out this.
I’ve broken the list into two groups, European and American. It’s sorted by engine, most engines were shared in numerous cars. Also the simplified with the highest rating.
Mercedes V8 - up to 300hp [in the 300SEL 6.3]
Jaguar V12 - up to 314hp [in the XJ-S]
Aston Martin I6 - up to 330hp [in the DB6 Vantage]
Maserati V8 - up to 335hp [in the Ghilbi SS and Bora SS]
Lamborghini V12 - up to 380hp [ in pretty much every early Lambo highest in the Miura SV]
Ferrari V12 - up to 400hp [In almost every 60s Ferrari highest in the 500 Superfast]
As for American cars we’ll set the bar a bit higher, here’s all the engines rated at over 400hp.
Oldsmobile 455 - up to 400hp [ highest in the 1970 Cutlass 442]
Cadillac 500 - up to 400hp [peaked in 1970]
Pontiac 421 - up to 405hp [1963 Super Duty]
Chevrolet 409 - up to 425hp [Bel Airs, Impalas, Biscaynes]
Ford 427 - up to 425hp (but probably more) [highest in the Thunderbolt, second highest in the Cobra]
Mopar 426 - up to 425hp (but probably more) [425 in everything]
Chevrolet 427 - up to 435hp [1967 Corvette only]
Chevrolet 454 - up to 450hp [1970 Chevelle, and like 2 Corvettes]
There’s A LOT of cars just under the 400 mark; Mopar 440 and 413, Pontiac 428 and 400, Ford 429, Cadillac 472, Chevy 396, and Olds 425 all made over 370hp. I don’t want hear about the Ford 427 sohc, that’s a pure race engine.