I've heard Westinghouse was also a vendor, but the numerous original '68-'69 Road Runners and Chargers I've seen & owned all had GEs in them, and all had the wide ribs on their lenses and had "GENERAL ELECTRIC" on the bottom.
They're ink-stamped on their backsides, but I never bothered decoding them. Even back in the '80s, they were hard enough to find; I used to bone them from the junkyards I visited.