The biggest problem on the 416 head is the exhaust port.
This is where you will go wrong buying into the "don;t hog it out advice"
The whole exhaust port needs a good bit of enlarging and shaping.
But,,, do not just make the port opening huge. As tempting as it might be.
Do not make the exhaust port exit larger than the headers are.
All you will do is make for leaky header gaskets.
The only time you need a large ex port exit is for a full race large diameter superstock header.
Again the meat and potatoes is deep in the port.
If you are not dirty up to the elbows, it ain;t enough.
Get serious around the guide boss in both the intake and exhaust port.