73 Roadrunner help! dash light question

I have a 73 Roadrunner factory 318 Auto car. In the center of the dash is two small holes for mounting?

Many have said, " Reverse indicator light". I read they only came in 4 speed cars? Some said, " Seatbelts light or defrost on light".

Here is a pic of my car can you please help me figure out what goes there and where I can find one?

Thanks Much, Troy