1979 Holden Premier 308 problems

Engine Mechanical problem
1979 Holden Premier V8 Two Wheel Drive Automatic

308 kingswood ute, fitted with a brand new holley street avenger 570, new plugs, leads, dizzy cap, problem starts and idles fine but when I accelerate it stalls so I pump it to keep it going, then when I run it under load it starts back firing out the exhaust, the timing is at 8 degrees tdc it has a electronic dizzy fitted there are no air leaks, does anyone have any brilliant ideas what might be wrong