It will not be covered in the Chevrolet Assembly Manual since it was part of the Body build by Fisher.
I also wish we had more part and piece construction details from the Fisher ide of the house, but the Body By Fisher service manual applies to many series of Chevrolet bodies it is of only so much value.
One "HACK" is to Request a Hard copy of the AMK catalog with one of your orders and it can be a visual aide in hardware identification and sourcing similar hardware that will perform same Form/Fit and Function.