I think the N-96 Shaker Hood option on the 1970 340 Cuda Convertible may be the rarest. As far as i can tell, they built 1. And i own it ( and had it researched/documented), so i think this is the case. If anyone knows differently, please let me know.
They built 22 total, of which 14 went on the hemi cuda convert. The other 8 were spread over the 340, 383, 440 and 440-6 (with most of the 8 going on the 440-6.
The word from a few retirees from the legal and engineering staff ( as i have come to learn) was a problem with decapitation. Once the hood was reinforced as the shaker hood was, it would not buckle on impact. The hood pins held it down. The A pillars could lay down on impact. I am told it happened .
That said, they redesigned the hood mid year to include "crumple zones" (aka 71 hood), and made only a couple cars at the end of the production year.