You've been there, so you know how the Poncho's responded. I had a hand in a half dozen or so 400/455 street builds. Not talking race builds, except for one round port, but the untouched "D" port heads just didn't respond to big lift cams. I learned my lesson the hard way with a 70' 400 that I built as a higher rpm engine. Lots of lift, a single plane, and a big carb (850). All I did was take away the torque and the heads just couldn't handle that style of build. Lost bottom end and top end...:banghead:.
As you said, if you didn't have a 10ish to one to begin with, it was gravy to just drop on a set of early 72cc heads to get the comp back. As long as you had the squeeze, a cam with 470"/490" lift and a moderate .050 duration, along with a dual plane to keep the torque up, resulted in a serious street player with a 3.55 or so gear.