The First 1967 383 A-Body, 'Barracuda or Mr. Norms's Dart'

Teak,

Arlen Vanke designed the original 1967 383 exhaust manifolds for the A-Body cars
in 1966 (late-August).

Castings #2899002 and #2863900

Later in 1967, the 'same' casting unit had design improvements, which helped improve
exhaust flow.

Hard to put an exact Horsepower Gain on the design improvement, but I would
guess between {7 to 11} 'added' Horsepower.