What you’re looking to do is play around with fuzzy math, that you can come up with arguments to compliment any result you may come to.

For example, you could conclude the power is limited by the lift, based on the flow at that point.
But...... if you kept the lift the same but made the CR 14:1 it would make more power without changing anything else.
Now, add duration....... more power. Add a vacuum pump..... more power.
Now add a 440-3x and an 1150 carb...... more power.
You could make 100hp more without changing the lift......... so was that really what’s holding it back?
.600 isn’t at all optimum....... but it’s certainly not the “wall”.

The dyno sheet is the report card on that overall combo, and there is no one magic silver bullet that’s going to transform it into something else.
As I see it, The three biggest culprits in the quest for power from that combo are the CR, the cam(and rocker ratio), and the carb.

I don’t have any ootb flow numbers for those heads, but with the seats recut and blended the intakes flowed:
Lift—— int
.100— 72
.200—145
.300—206
.400—261
.500—304
.600—353
.700—381
.800—384

The motor these heads were on made 918hp, and the car it was in went 8.33@165@2700lbs