Is the miss at idle only or all speeds? How is the overall performance?

Have you checked the carb's idle circuit, metering and main jets for debris? Is the carb adjusted and tuned correctly? Have you checked the fuel filter? Have you checked the fuel pressure? Have you checked manifold vacuum with a gauge?

Have you read the plugs? Do you have the correct heat range plugs?

Is the coil getting consistent input voltage (12v)? Are any plug wires too close to the exhaust manifolds? Are plug wires touching and crossing each other?

Does your exhaust system have any restrictions in it?