What is enough vacuum for power brakes?

Restoring a 71 Dodge Demon. It has a 440 Big Block 4 Speed. It has the Kelsey Hayes 4 Piston calipers up front and I swapped out the rear drums and shoes for 10 inch. I have replaced the Proportioning valve and all the metal and rubber lines calipers and shoes and hardware.

I had a hard time bleeding the brakes (Vacuum bled, gravity, 2 man) I finally was able to get a good pedal but when we road tested the car it seems to stop normally but if I try a panic stop or press the brake pedal a couple times the pedal feels hard and the car will keep rolling.

The engine has been rebuilt and was bored 40 over, crank 20 under, flat top pistons w/valve reliefs and a Comp Cams 292H Grind. Duration 290 (@.050 lift 244) Valve Lift 0.501

My question
Is this cam creating enough vacuum to the brake booster?
If not besides going to manual disc brakes is there any way to correct this?

I am running the Single Diaphragm Booster but starting to wonder about the Master Cylinder I was sold