The ’77 uses these side brackets to support the grille, but they can be easily unbolted. It would be tough to retrofit them to the core support of an older truck. The core supports for the ’73-’76 trucks we saw had nonremovable grille brackets at both sides of the radiator. Swapping them onto the ’77 would require changing the entire core support, so we just skipped it and hung the grille with fewer screws. The ’73-’76 grille brackets didn’t look like they’d get in the way of installing a newer ’77-’79 grille.