Sorry to hear about your engine woes. I hope you can get it nailed down without too much trouble/expense. If you want dual carbs, go for it. It's my favorite look, and I don't care if it's an S/C type car. Unless you are tracking/racing that car, tuning it for street gas and street use might provide you with more enjoyment. Forget about chasing horsepower numbers. There is enough power to weight ratio to kill you with half the potential power of that FE.
Not a CSX, but I have had the pleasure to own 2 ERA 427s with the dual carb setup and I find myself peeking under the hood WAY TOO often. Hell, I take the garbage out, the car catches my eye and I lift up the hood and I feel better that day!
Both of these setups used the late model Holley 600s that Dan mentioned here. The original Ford matching carbs and intake is VERY expensive. An old school mechanic can tune your dual carb setup to perfection and you will not have to worry about it too much. As Dan said, the green foam air cleaners are restrictive (so are side pipes), so don't spend an extra 10K chasing horsepower in your engine build if the car can't breathe! On the red car below I found some WIX filters at the auto store that were not very expensive. A bit taller than the green foam, but I removed the outer metal grille from the S&H filters and carefully fit it over the new paper filters. It fits pretty well and I'm satisfied with the setup.
