The switch is the same and the wiring is probably the same but when the high beams are turned on in a quad lamp system, all four headlamps are on.
Are you sure about that? I don't have an example, but on a 55.2 truck (2 headlamp system) and 59 truck (4 headlamp system) with the same switch and wiring, that can't happen. Maybe on SOME 4 headlamp systems that's true, but not on a Chevy truck.
The individual filaments are NOT on at the same time in a 2 headlamp system. Maybe done that way to prevent excess heat which would cause shortened life of the bulb.
