Alan,
what is the set-up of the rest of the motor? Stock cam? auto? power brakes? Does the surging or any erratic running occur at idle? In and/or out of gear? ( if auto ). What ignition are you running? Did you have six pack carbs on there before? And, if so, did they run bad? Hence, the new ones.

What I am getting at is if there's another reason for the surging, like a vacuum leak. I usually isolate the carbs as much as possible when trouble shooting. The car