#1 > Try to get some Part #'s off the Carburetor and Distributor. #2 > Get that 'timing' down a bit, and see if the knocking persists. #3 > Get the highest rated Octane Gas as possible in that Fuel Tank. #4 > Pull the Spark Plugs, and inspect {color and gap}. #5 > Compression Test {see what those cylinders are pumping} #6 > What Temperature is the engine coolant reading at.
Note; The 'Mechanical Advance' Distributor may be the problem here.