When I looked that cam up on the comp website they had a Dino pull and it showed just about the same results you had. On a mildly built engine.. I think it said something about Dart RT heads or something?
My cam has just about the same lift(after its last regrind), but I'm using 1. 6 to 1 rocker so I get a little bit more out of it. also my duration has another 10 degrees at least at 50..
Again I never bought the Speedmaster heads trying to light the world on fire or take me to the next level... I've always wanted aluminum heads and always looked at the Edelbrocks but could never afford to pull the trigger.. if I'm anywhere in the ballpark out-of-the-box I'll be plenty happy....