I think the tests I did on my own 383 proved that to be the case.
A properly machined and assembled long block, with a cam(granted, a pretty good sized one), intake, carb, and headers making 475+ hp.
Heck, it made 420hp with just the cam and headers……stock intake and carb.
Say you installed a streetable cam and it lost as much as 35-40hp……it would still be nearly 1 hp/ci.
That’s not terrible imo.