Correct........
The 452's were the first set of heads my son and I used for a performance build. He asked for us to build a performance engine together after he found an article in Dec 1982 Popular Hot Rodding that featured a 440 that his grandpa (my dad of course) had built. He wanted to do the same thing. So I told him we needed cylinder heads to proceed.
He spent somewhere between 9-12 months, a full pallet of cut up, drilled to swiss cheese and band-sawed in half iron cylinder heads, of which, three were Stage V heads, one to practice on and two to use. He destroyed all three Stage V's.
The flow bench he used was some 4 miles from the porting room (a single car garage on 4 acres), so it really was a herculean effort.
Eventually he brought me the 452's and said, "What about these?" Well, 588 tq and 621 hp.
The project evolved until the little 451 stroker made 787 HP on 91 octane pump gas with Edelbrock 84cc 440 RPM cylinder heads. His porting of course.