Are you running the car on the factory tank or a gas can? Did the car have old gas in it? or is it a new tank with new gas?

Are all the grounds good on the ignition box, motor, and battery?

Did the carb sit for a long period of time with old gas in the bowls? Are the carb butterflies closed all the way or hung up on a gasket?

Did you try spraying carb cleaner around the intake and carb bases to check for a air leak?

Are the sparkplug wires tight on the plugs, maybe a bad set of wires even though they are new?