It could be a vacuum leak around the base of the carb, and if it is popping back through the carb on hard accel it could be the intake gaskets. I had some gaskets do that years ago when I swapped intakes. Since then I use Victor or FelPro and havent had it happen since. The carb cleaner trick around the base and manifold might show it.
Surging is a lean condition, it could just be some crud in the carb, or it could be a bigger problem. One thing you can try is to remove the air filter housing, rev the engine up above idle, say to around 3000 or 3500, then cover the primary side with your hand so it creates a suction. Be careful, you can get a laceration from a high vacuum engine. When it starts to die off, move your hand and let it come back. Do that a few times, you should get black smoke from the tail pipes when you do it right. Doing that will suck all the varnish and crud from the gas out of the small passages. If that doesnt fix it then its time to pull the top and take a look.
Since you did a cam swap, my guess is a vacuum leak somewhere. That will make a lean condition real quick. The E carbs are so simple with few small passages, compared to a Qjet, that I would tend to look for leaks first.