engine breaking up at low end

I'd start by pulling all the plugs and checking to see if one of them has been miss firing. 1 might be black and rest brown around the electrode. Check all your wires to make sure that they're making good contact. Pull the distributor cap and look for carbon tracking on the inside. Are you getting black smoke out the exhaust at low RPM, if so primary side is to rich which you'll also see by looking at the spark plugs, they'll all be black. It could even be a problem with the ignition coil but these usually crap out at high RPM.

It could also be that that single plane intake is fighting with your cam in which case a 1 inch 4 hold carb spacer might clean up the bottom end, it worked on my BB.

Terry