well there weren't any fiberglass trucks in our era and all the big bulbs I've seen have 3 pins the same size, but an ebay look finds H4 connectors with colored wires that show the black on the right
"When we tug a single thing in nature, we find it attached to the rest of the world" ~ John Muir "When we tug a single thing on an old truck, we find it falls off" ~ me Some TF series details & TF heater pics
and all the big bulbs I've seen have 3 pins the same size, but an 
