Not to jump away from the discussion.
But my mother bought a new 1970 Duster 340 - 4-Speed with the standard 3.23 Sure-Grip
off the 'showroom floor' from Mahopac Chrysler-Plymouth in May 1970.
A few months later, after the 'break-in period', my father took it out for it's 'Maiden Voyage' at Dover Drag Strip.
Ran a best of 14.41 @ 97 MPH, and won a Class Trophy in 'G/S'.
I saw it, and can atest, that no 'stock' 383 Road Runner 4-Speed could ever do that with 3.23 Gears.