If you look at the Chevrolet Historical website there are two distinct downloads on a year such as 1964. They have they're own data different obviously from the C or K models.
Truck -
https://www.gmheritagecenter.com/doc...olet-Truck.pdf
El Camino -
https://www.gmheritagecenter.com/doc...-El-Camino.pdf
And it that download on page 41 is the Chevelles, part of the El Camino information download.
However they do list them in the truck section.
Just not a C10 or K10 by any stretch of the imagination.
87-91 GM Squarebodies are R and V series but they are allowed in the C and K forums. We even have a forum for Isuzus with Chevy Luv Badges on them.