Slick 60's

My headlights briefly went out twice this weekend driving back home in about 45 minutes. First time it was virtually instantaneous and second time was about 4 seconds. I have a new replacement headlight switch as well as a high/low beam switch. Lights are nice and bright and haven't been converted to halogens. I don't drive much at night so this may not be a new problem. I noticed that '61 has a different part number than '62-'64. Does anyone know what the difference may be?

61-64 have the fuses on the bottom with a short shaft pull knob
65 and 66 have a separate fuse box and a longer shaft on the pull knob.

i do not know any difference between 61 and 62-64 .
also, LMC lists the switch as 61-64: