First of all, I approve of the chop at idle. That's some aggressive cam lift & timing and I'm all here for it. We don't have those big displacements over on our side of the pond and I love 'em dearly...
The Boss 429 engine used a single Holley four-barrel carburetor rated at 735 CFM mounted on an aluminum intake manifold. All these cars had 4-Speed Manual Transmissions and the Boss was rated very conservatively at 375 HP while actual output was believed to be well over 500 horsepower