Not to muddy things up but on my 68 B the parking lights go out when I turn on the headlamps by design. I also have a 64 A and I replaced the H/L switch as they cut out driving at night.....turned out to be the connection at the floor dimmer switch which h/l juice goes through. All cruddy and corroded . Anyway the SMP h/l switch dash dimmer was very hard to turn and the dash lights were off. I was afraid to turn it the knob that hard for fear of breaking it but it's works fine now . I nterior lights now turn on with an audible click. Have you looked at the directional switch? Rear stuff goes through that too I believe.