Measure idle vacuum, fully warm, in Park. For a stock engine, it should be at least 18", and closer to 20" If not, you have a vacuum leak.
I've had several "rebuilt" carbs run like crap in the idle circuit. Half the time, they missed cleaning something out, or something is clogged in the idle circuit. If it's not carb related, I would look at ignition. Are your vacuum lines routed to factory spec? Sometimes if you run vac advance to manifold vacuum, it will pull too much advance at idle and cause a rough running condition. It could also be a burned valve.
Original carburetor idled rough, and then the rebuilt ran the same. Most common cause is vacuum leak. Could be the things you mentioned, but less likely.
Start by using a timing light to confirm each plug wire is getting power. And pull all Of the plugs and inspect.
