I kept forgetting to check my 69 but I finally did last night. I have splash shields on both sides of my fender extensions. I also have an old one that I took off my parts car. I'll post some pics tonight if I remember.

So.....maybe we should consider a 6th splash shield instead of just 5. This may be one of those parts that the plant randomly did not put on or only put one on or put both on. A better guess maybe that they were lost if your car was ever disassembled in its life.