I was doin a little searching on eBay and came accross an NOS headlight switch for a 69 Chevelle. Then the ad says that it also fit 1968 Chevelle. Then it says it also fits 64 65 66 67 Chevelles.
Ok, so the 64-69 Chevelle's take the same headlight switch. Great !

It's part # 1995178 or D1590

So I decide to do a search for these numbers.
You won't believe what I found.
This particular headlight switch fit's a multitude of other cars and IH trucks. Yes, that's right International Harvester trucks. Scouts, etc.

Check out this auction. #8056900322

Now it's getting confusing.
Check out auction # 320001939772

I makes sense that a part like a switch would fit a multitude of cars, especially across the GM line. If each part was car specific, cars would cost a fortune, and more importantly, most of our older cars could not be repaired.

Image if tires were car specific, or batteries or spark plugs!

Just a hint, its easy to copy and paste a link.

My 64 has one out of a 77 Nova. It looked like it was replaced in the Nova at the junkyard, so I nabbed it.