New to carbed engines, need some SBC misfire help

[Fangio]

First time messing with a carburated engine and need some help troubleshooting. Its a 64 lwb with a Chevy 350 with turbo 350 trans. Engine always starts on first crank and idles great but while accelerating at anything greater than half throttle the engine sputters and misfires. If I back off the throttle it continues to accelerate without issue. It has an edelbrock performer 600 with electronic ignition. Previous owner said he installed new spark plugs adjusted valves, and set timing. All the vacuum lines look to be in good shape as do the plug wires. I haven't spent much time looking at it yet but my initial thought is timing. Any other ideas or maybe a good plan of attack? Thanks in advance.