Surging is typically associated with too little fuel, I would confirm the ignition system is 100%, then work on the fuel system. Make sure the fuel lines are clear and tight and not sucking air into the system, check pressure AND volume of the pump, then work on the carburetor.
1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy
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