They are also for accessing the retracters and cables for a clam shell rear door set up. One of the forward holes gets you to the retracter mounting point. The rearward one gets you to where the cable meets the retracter tape. Without looking at it, I can't remember which is which. If you have barn doors you won't have to worry about it.
I'm in the process of trying to find cables for my 58 Burb with a clam shell rear door.
