Carter AVS on a 340 drains of fuel

Is your tank vented , I have seem where it was not vented and would have a vacuum on tank. I had a demon carb on my challenger no problem, changed to a eldebrock 800 next morning no start. put a good space under and it helped a lot.
Tank is vented. Even replace the vent tube with a new one. IF I was to change the carb, any recommendations Holley vs Edlebrock. I would like to go with one that would bolt right on to the stock manifold without an adapter plate if possible. By the way, thanks for all the input guys. This has been very helpful.