My tri-power Goat (GTO) was easy to tune...progressive linkage, so the car ran on the center carb until you hit the loud pedal. Then the other two would kick in. The lingo of the day: "six pack" was MOPAR..."tri power" was GM. I'm doing a bit of guessing now...if memory serves, when all three of my carbs were open, the flow was around 1400 cfm? Today, a single 4 barrel and single plane manifold will produce more power due to design advances in both carbs and manifolds. But, ohhh the harmonics of a multi carb set-up at full tilt boogie! It was glorious!
If I'm not mistaken, nostalgia buffs can now find triple carb manifolds new.