Have you checked the points, and dwell angle? if this is way off it can cause misfires and rough running. If you have a dwell meter, set the dwell angle to between 48 and 52. At least check the surfaces of the contacter faces. Make sure they are not too pitted. Im not sure what the points gap should be if you dont have a meter. Maybe about .5mm-.7mm? Someone else here will know the right gap setting.

Once the points are set. the timing will have to be redone.