According to Chevy literature, some time in mid-year '51, all deluxe options, the chrome grille, and RPO rear bumper were discontinued, and gray paint replaced chrome on front bumpers and hubcaps. So if a late '51-'53 has a chrome grille, bumper, and/or hubcaps, they aren't original. I'd assume GMC was under similar restrictions, but I can't say for sure. Chrome items returned in '54.
A '49-mid-'51 chrome grille would have had the Waldorf White inner bars, same as the body color grilles.