71 383 w/AVS. Engine stumbles initially, but if I keep the throttle open, it picks up again & pulls pretty hard. I've tried adjusting the accelerator pump in each direction & neither position stopped the stumble.

I'm starting to lean toward an ignition problem. The plugs were really fouled from a previously corrected problem, so I cleaned 'em up with carb cleaner & a wire brush. My timing light also seems to have a problem triggering off the ignition wires (the light works just fine on my factory wired Dodge Ram). I guess I'm just not sure it's a weak spark since I wouldn't expect it to pull hard after a couple of seconds of sumbling.

Any ideas?