When good is not enough, Camshaft time again.

JMO, no chance I run that set up with less than 600-650 lift.

That cam change is minor IMO. Some more data acquisition prior to tear down, like the vacuum at high RPM during a full run in each gear would have told you a bunch. Supporting 650hp is not the same as allowing sufficient airflow into the engine. Thus, my suggestion regarding the vacuum reading in high gear full throttle top of pull. Marathon runner having to run breathing through only a straw.

Hope it works. Find someone with a true 1000-1050 cfm carb that is good if these change results aren't up to snuff.

Good luck with it and have fun, that's what counts.