That's great that you found NOS parts. It may not seem significant, but even a minor keyway change can make a big difference. I was wondering if you degreed the cam with a factory timing set for comparative purposes. I didn't mean ignition timing, sorry if I was unclear on that.

There is a point at which knock occurs, temperature, pressure and fuel are the factors involved. Cam timing and compression ratio control the pressure, user controls the fuel, and there are various ways to control the temperature. I haven't yet found cranking cylinder pressures from a 1969 400 road test, if anyone has them please share.