From this photo in the CRG assembly process article, the buck-built front end was assembled with much of the grille components and headlights, so the build configuration including paint color, any striping, std or RS grille and headlights and hood style would be significant during that sub-assembly, as well as the fender piercing already discussed.
The ident number can be seen on the driver side of the firewall, so a corresponding number on the front end seems logical.
Image reposted from the CRG site.