There's usually a ground pigtail from each headlight socket-plug (or at leat one-per side on four-headlight systems); it usually attaches to the fender or fender apron or radiator core-support behind the headlight shell or near the bucket, often with a sheetmetal screw.
If the front sheetmetal is kind of crusty and your headlights are seem dim, it sometimes helps to run a #12 or #14 ground wire from the various fender aprons (or wherever the front lights ground to) back to the battery ground conection or to the engine block.
Vehicles that depend upon "chassis grounds" often find those grounds compromised after 30-50 + years of corrosion.
Freshly painted panels painted separately, then bolted together may also not make good chassis grounds.
Good luck !
