Lets see if i remember this correctly? Rectangular tailights on on the first and second group of 427's.
CSX 3000's and CSX 3100's. I believe the round tailights begin somewhere in the CSX 3200's and are used until the end of production.
The "narrow hip 427's" are a group of I think 25 cars in the CSX 3100's. I want to say in the 3125 to 3150 or so but in that area rather then the end of the 3100's.
Apparently they were a "test run" of sorts to gauge customer opinion as an alternative to the big rear flares and the 7" wide Sunburst wheels.
The narrow fender cars got voted off of the island.
I do remember a period of time in the early '70s when "Cobra discovery" was going on and some were questioning the narrow hip cars as not original cars.
I remember Tony Hogg having a silver one while he was editor of Road & Track mag. I think it was a CSX3140 something car? Maybe 3142?
I used to be able to do this without a Registry. I'm sure Ned still can? Is time and distance the same as old age and senility?