This is one of my older post but I solved it. I found a non-AC dash to replace mine. No more AC vent holes. I'll clean it up and paint it to match as close as possible. A pic will be posted tonight.
Glad your problem is fixed. I didn't read this thread, but did you ever think about just getting a replacement vent and putting it in? I don't have A/C in the Bronco (I could, but removed the system) and still have my middle vent sitting in there.
I just read this post for the 1st time today also. I would have offered you the vents. I have the middle and pass side out of a parts truck I had. You can still have them if you dont want to swap dash's.