318 Engine stumble

Around 15-1700 rpm.....huge stumble
When I get pst it the power is there


In neutral
Slowly raising gas......stumble occurs like a surge. Starting about 15-1700
And doesn't go away

Vac at idle is 19
Timing 8°

318 1976 stock and original everything
Holley 600 vac sec

1968 points distributor