Kevin.
A long time ago, when I too was in Florida ( one of those rare things, a native Floridian ) my daily driver '70 440 six pack Charger R/T use to give me the same issue. For me, it wasn't the carbs, it was the ignition. When I ran the new electronic Direct Connection distributor with the vacuum advance hooked up, my timing was way too high, hence the surging. When I took the vacuum line off and just plugged off ports, it went away. I see you're running a single point. When you have the car in park, have you checked the timing mark when you have the engine running at cruising rpm's? What I'm getting at is see if your timing mark is fluctuating or if it is steady ( as it probably should ). As you have built many carbs before, they are relatively simplistic. I don't think the .484 is too much that the jets in the center carb can't feed it at cruising speeds. You are looking down into the center carb to see if the flow of fuel pouring out of the ventures is reasonable? Granted, there's no way of verifying proper flow by a visual. As you pointed out, plugs are a good indicator..