Sorry looked at the different pictures and missed in the first one the side by side holes and your clear mention that they were horizontal. Dealing with a bit of Covid at the moment so I must not be reading so posts completely enough.
With that said you posted just pictures of empty holes taken of your car. Since your ownership has anything been mounted or located in those holes or are we assuming that they were the double warning lights?
I have to admit i missed this detail when I acquired the car two plus years ago. I literally flew up to meet the seller, had the transporter there that afternoon and flew back the next day. The car was delivered to my restorer. I never actually sat in the darn thing. Its now 2 ? years later and i am still combing out the details. All of the pre-disassembly pics I have just show parts of hols with no lights installed. Nothing has ever been installed in those holes.
Based on the deluxe Marti Report both lights are supposed to be there. The hole sizes appear to the the approximate correct size. Midlife has a good point. This car was scheduled to be built 7/4/68. But not built until lAugust, I think. Just in time to be shipped out as 1 of 10 for the show circuit. So they could have been just jaming things in to get them out the door as Midlife referenced in his post.
Car is auto with tach, FYI.